diff --git a/src/Controller/AdminPages/BaseAdminController.php b/src/Controller/AdminPages/BaseAdminController.php
index 92f6ee07..cf856e8f 100644
--- a/src/Controller/AdminPages/BaseAdminController.php
+++ b/src/Controller/AdminPages/BaseAdminController.php
@@ -29,6 +29,7 @@ use App\Entity\Base\AbstractNamedDBElement;
 use App\Entity\Base\AbstractPartsContainingDBElement;
 use App\Entity\Base\AbstractStructuralDBElement;
 use App\Entity\Base\PartsContainingRepositoryInterface;
+use App\Entity\LabelSystem\LabelProcessMode;
 use App\Entity\LabelSystem\LabelProfile;
 use App\Entity\Parameters\AbstractParameter;
 use App\Entity\UserSystem\User;
@@ -159,7 +160,7 @@ abstract class BaseAdminController extends AbstractController
         //Disable editing of options, if user is not allowed to use twig...
         if (
             $entity instanceof LabelProfile
-            && 'twig' === $entity->getOptions()->getProcessMode()
+            && LabelProcessMode::TWIG === $entity->getOptions()->getProcessMode()
             && !$this->isGranted('@labels.use_twig')
         ) {
             $form_options['disable_options'] = true;
diff --git a/src/Controller/LabelController.php b/src/Controller/LabelController.php
index 36f9b669..7d98019d 100644
--- a/src/Controller/LabelController.php
+++ b/src/Controller/LabelController.php
@@ -43,6 +43,7 @@ namespace App\Controller;
 
 use App\Entity\Base\AbstractDBElement;
 use App\Entity\LabelSystem\LabelOptions;
+use App\Entity\LabelSystem\LabelProcessMode;
 use App\Entity\LabelSystem\LabelProfile;
 use App\Entity\LabelSystem\LabelSupportedElement;
 use App\Exceptions\TwigModeException;
@@ -81,7 +82,7 @@ class LabelController extends AbstractController
         $label_options = $profile instanceof LabelProfile ? $profile->getOptions() : new LabelOptions();
 
         //We have to disable the options, if twig mode is selected and user is not allowed to use it.
-        $disable_options = 'twig' === $label_options->getProcessMode() && !$this->isGranted('@labels.use_twig');
+        $disable_options = (LabelProcessMode::TWIG === $label_options->getProcessMode()) && !$this->isGranted('@labels.use_twig');
 
         $form = $this->createForm(LabelDialogType::class, null, [
             'disable_options' => $disable_options,
diff --git a/src/Controller/ProjectController.php b/src/Controller/ProjectController.php
index a15ce97f..08ddc258 100644
--- a/src/Controller/ProjectController.php
+++ b/src/Controller/ProjectController.php
@@ -176,9 +176,9 @@ class ProjectController extends AbstractController
                     return $this->redirectToRoute('project_edit', ['id' => $project->getID()]);
                 }
 
-                if (count ($errors) > 0) {
-                    $this->addFlash('error', t('project.bom_import.flash.invalid_entries'));
-                }
+                //When we get here, there were validation errors
+                $this->addFlash('error', t('project.bom_import.flash.invalid_entries'));
+
             } catch (\UnexpectedValueException|SyntaxError $e) {
                 $this->addFlash('error', t('project.bom_import.flash.invalid_file', ['%message%' => $e->getMessage()]));
             }
diff --git a/src/Controller/WebauthnKeyRegistrationController.php b/src/Controller/WebauthnKeyRegistrationController.php
index f2323510..5f2e3e9b 100644
--- a/src/Controller/WebauthnKeyRegistrationController.php
+++ b/src/Controller/WebauthnKeyRegistrationController.php
@@ -77,9 +77,14 @@ class WebauthnKeyRegistrationController extends AbstractController
                 return $this->redirectToRoute('webauthn_register');
             }
 
+            $user = $this->getUser();
+            if (!$user instanceof User) {
+                throw new RuntimeException('This controller only works only for Part-DB User objects!');
+            }
+
             $keyEntity = WebauthnKey::fromRegistration($new_key);
             $keyEntity->setName($keyName);
-            $keyEntity->setUser($this->getUser());
+            $keyEntity->setUser($user);
 
             $em->persist($keyEntity);
             $em->flush();
diff --git a/src/DataTables/Filters/Constraints/EntityConstraint.php b/src/DataTables/Filters/Constraints/EntityConstraint.php
index 40293e02..7365890b 100644
--- a/src/DataTables/Filters/Constraints/EntityConstraint.php
+++ b/src/DataTables/Filters/Constraints/EntityConstraint.php
@@ -96,6 +96,7 @@ class EntityConstraint extends AbstractConstraint
 
     /**
      * Checks whether the constraints apply to a structural type or not
+     * @phpstan-assert-if-true AbstractStructuralDBElement $this->value
      */
     public function isStructural(): bool
     {
diff --git a/src/DataTables/ProjectBomEntriesDataTable.php b/src/DataTables/ProjectBomEntriesDataTable.php
index 1870c262..dec3ea1e 100644
--- a/src/DataTables/ProjectBomEntriesDataTable.php
+++ b/src/DataTables/ProjectBomEntriesDataTable.php
@@ -95,6 +95,8 @@ class ProjectBomEntriesDataTable implements DataTableTypeInterface
                         }
                         return $tmp;
                     }
+
+                    //@phpstan-ignore-next-line
                     throw new \Exception('This should never happen!');
                 },
             ])
diff --git a/src/Entity/Attachments/Attachment.php b/src/Entity/Attachments/Attachment.php
index 06e7fdd6..270e3c5b 100644
--- a/src/Entity/Attachments/Attachment.php
+++ b/src/Entity/Attachments/Attachment.php
@@ -110,7 +110,7 @@ abstract class Attachment extends AbstractNamedDBElement
     protected bool $show_in_table = false;
 
     #[Assert\NotNull(message: 'validator.attachment.must_not_be_null')]
-    #[ORM\ManyToOne(targetEntity: 'AttachmentType', inversedBy: 'attachments_with_type')]
+    #[ORM\ManyToOne(targetEntity: AttachmentType::class, inversedBy: 'attachments_with_type')]
     #[ORM\JoinColumn(name: 'type_id', nullable: false)]
     #[Selectable()]
     protected ?AttachmentType $attachment_type = null;
diff --git a/src/Entity/Attachments/AttachmentType.php b/src/Entity/Attachments/AttachmentType.php
index 72752a72..6314fe7c 100644
--- a/src/Entity/Attachments/AttachmentType.php
+++ b/src/Entity/Attachments/AttachmentType.php
@@ -43,11 +43,11 @@ use Symfony\Component\Validator\Constraints as Assert;
 #[ORM\Index(name: 'attachment_types_idx_parent_name', columns: ['parent_id', 'name'])]
 class AttachmentType extends AbstractStructuralDBElement
 {
-    #[ORM\OneToMany(targetEntity: 'AttachmentType', mappedBy: 'parent', cascade: ['persist'])]
+    #[ORM\OneToMany(targetEntity: AttachmentType::class, mappedBy: 'parent', cascade: ['persist'])]
     #[ORM\OrderBy(['name' => 'ASC'])]
     protected Collection $children;
 
-    #[ORM\ManyToOne(targetEntity: 'AttachmentType', inversedBy: 'children')]
+    #[ORM\ManyToOne(targetEntity: AttachmentType::class, inversedBy: 'children')]
     #[ORM\JoinColumn(name: 'parent_id')]
     protected ?AbstractStructuralDBElement $parent = null;
 
@@ -76,7 +76,7 @@ class AttachmentType extends AbstractStructuralDBElement
     /**
      * @var Collection<Attachment>
      */
-    #[ORM\OneToMany(targetEntity: 'Attachment', mappedBy: 'attachment_type')]
+    #[ORM\OneToMany(targetEntity: Attachment::class, mappedBy: 'attachment_type')]
     protected Collection $attachments_with_type;
 
     public function __construct()
diff --git a/src/Entity/Base/AbstractNamedDBElement.php b/src/Entity/Base/AbstractNamedDBElement.php
index 20009658..e5e30441 100644
--- a/src/Entity/Base/AbstractNamedDBElement.php
+++ b/src/Entity/Base/AbstractNamedDBElement.php
@@ -22,6 +22,7 @@ declare(strict_types=1);
 
 namespace App\Entity\Base;
 
+use App\Repository\NamedDBElementRepository;
 use Doctrine\DBAL\Types\Types;
 use App\Entity\Contracts\NamedElementInterface;
 use App\Entity\Contracts\TimeStampableInterface;
@@ -32,7 +33,7 @@ use Symfony\Component\Validator\Constraints as Assert;
 /**
  * All subclasses of this class have an attribute "name".
  */
-#[ORM\MappedSuperclass(repositoryClass: 'App\Repository\NamedDBElement')]
+#[ORM\MappedSuperclass(repositoryClass: NamedDBElementRepository::class)]
 #[ORM\HasLifecycleCallbacks]
 abstract class AbstractNamedDBElement extends AbstractDBElement implements NamedElementInterface, TimeStampableInterface, \Stringable
 {
diff --git a/src/Entity/Parts/Category.php b/src/Entity/Parts/Category.php
index 2f4b2d08..e5e3320e 100644
--- a/src/Entity/Parts/Category.php
+++ b/src/Entity/Parts/Category.php
@@ -45,11 +45,11 @@ use Symfony\Component\Validator\Constraints as Assert;
 #[ORM\Index(name: 'category_idx_parent_name', columns: ['parent_id', 'name'])]
 class Category extends AbstractPartsContainingDBElement
 {
-    #[ORM\OneToMany(targetEntity: 'Category', mappedBy: 'parent')]
+    #[ORM\OneToMany(targetEntity: self::class, mappedBy: 'parent')]
     #[ORM\OrderBy(['name' => 'ASC'])]
     protected Collection $children;
 
-    #[ORM\ManyToOne(targetEntity: 'Category', inversedBy: 'children')]
+    #[ORM\ManyToOne(targetEntity: self::class, inversedBy: 'children')]
     #[ORM\JoinColumn(name: 'parent_id')]
     protected ?AbstractStructuralDBElement $parent = null;
 
diff --git a/src/Entity/Parts/Footprint.php b/src/Entity/Parts/Footprint.php
index 8ec1bc35..8138f967 100644
--- a/src/Entity/Parts/Footprint.php
+++ b/src/Entity/Parts/Footprint.php
@@ -43,11 +43,11 @@ use Symfony\Component\Validator\Constraints as Assert;
 #[ORM\Index(name: 'footprint_idx_parent_name', columns: ['parent_id', 'name'])]
 class Footprint extends AbstractPartsContainingDBElement
 {
-    #[ORM\ManyToOne(targetEntity: 'Footprint', inversedBy: 'children')]
+    #[ORM\ManyToOne(targetEntity: self::class, inversedBy: 'children')]
     #[ORM\JoinColumn(name: 'parent_id')]
     protected ?AbstractStructuralDBElement $parent = null;
 
-    #[ORM\OneToMany(targetEntity: 'Footprint', mappedBy: 'parent')]
+    #[ORM\OneToMany(targetEntity: self::class, mappedBy: 'parent')]
     #[ORM\OrderBy(['name' => 'ASC'])]
     protected Collection $children;
 
diff --git a/src/Entity/Parts/Manufacturer.php b/src/Entity/Parts/Manufacturer.php
index c5b45bcd..b6768e4a 100644
--- a/src/Entity/Parts/Manufacturer.php
+++ b/src/Entity/Parts/Manufacturer.php
@@ -43,11 +43,11 @@ use Symfony\Component\Validator\Constraints as Assert;
 #[ORM\Index(name: 'manufacturer_idx_parent_name', columns: ['parent_id', 'name'])]
 class Manufacturer extends AbstractCompany
 {
-    #[ORM\ManyToOne(targetEntity: 'Manufacturer', inversedBy: 'children')]
+    #[ORM\ManyToOne(targetEntity: self::class, inversedBy: 'children')]
     #[ORM\JoinColumn(name: 'parent_id')]
     protected ?AbstractStructuralDBElement $parent = null;
 
-    #[ORM\OneToMany(targetEntity: 'Manufacturer', mappedBy: 'parent')]
+    #[ORM\OneToMany(targetEntity: self::class, mappedBy: 'parent')]
     #[ORM\OrderBy(['name' => 'ASC'])]
     protected Collection $children;
 
diff --git a/src/Entity/Parts/MeasurementUnit.php b/src/Entity/Parts/MeasurementUnit.php
index 62a3dd82..054056a8 100644
--- a/src/Entity/Parts/MeasurementUnit.php
+++ b/src/Entity/Parts/MeasurementUnit.php
@@ -74,11 +74,11 @@ class MeasurementUnit extends AbstractPartsContainingDBElement
     #[ORM\Column(type: Types::BOOLEAN, name: 'use_si_prefix')]
     protected bool $use_si_prefix = false;
 
-    #[ORM\OneToMany(targetEntity: 'MeasurementUnit', mappedBy: 'parent', cascade: ['persist'])]
+    #[ORM\OneToMany(targetEntity: self::class, mappedBy: 'parent', cascade: ['persist'])]
     #[ORM\OrderBy(['name' => 'ASC'])]
     protected Collection $children;
 
-    #[ORM\ManyToOne(targetEntity: 'MeasurementUnit', inversedBy: 'children')]
+    #[ORM\ManyToOne(targetEntity: self::class, inversedBy: 'children')]
     #[ORM\JoinColumn(name: 'parent_id')]
     protected ?AbstractStructuralDBElement $parent = null;
 
diff --git a/src/Entity/Parts/PartLot.php b/src/Entity/Parts/PartLot.php
index 15cda250..04cc726d 100644
--- a/src/Entity/Parts/PartLot.php
+++ b/src/Entity/Parts/PartLot.php
@@ -79,7 +79,7 @@ class PartLot extends AbstractDBElement implements TimeStampableInterface, Named
      * @var Storelocation|null The storelocation of this lot
      */
     #[Groups(['simple', 'extended', 'full', 'import'])]
-    #[ORM\ManyToOne(targetEntity: 'Storelocation')]
+    #[ORM\ManyToOne(targetEntity: Storelocation::class)]
     #[ORM\JoinColumn(name: 'id_store_location')]
     #[Selectable()]
     protected ?Storelocation $storage_location = null;
@@ -110,7 +110,7 @@ class PartLot extends AbstractDBElement implements TimeStampableInterface, Named
      * @var Part The part that is stored in this lot
      */
     #[Assert\NotNull]
-    #[ORM\ManyToOne(targetEntity: 'Part', inversedBy: 'partLots')]
+    #[ORM\ManyToOne(targetEntity: Part::class, inversedBy: 'partLots')]
     #[ORM\JoinColumn(name: 'id_part', nullable: false, onDelete: 'CASCADE')]
     protected Part $part;
 
diff --git a/src/Entity/Parts/PartTraits/BasicPropertyTrait.php b/src/Entity/Parts/PartTraits/BasicPropertyTrait.php
index 192531e3..b0f593d6 100644
--- a/src/Entity/Parts/PartTraits/BasicPropertyTrait.php
+++ b/src/Entity/Parts/PartTraits/BasicPropertyTrait.php
@@ -66,7 +66,7 @@ trait BasicPropertyTrait
     #[Assert\NotNull(message: 'validator.select_valid_category')]
     #[Selectable()]
     #[Groups(['simple', 'extended', 'full', 'import'])]
-    #[ORM\ManyToOne(targetEntity: 'Category')]
+    #[ORM\ManyToOne(targetEntity: Category::class)]
     #[ORM\JoinColumn(name: 'id_category', nullable: false)]
     protected ?Category $category = null;
 
@@ -74,7 +74,7 @@ trait BasicPropertyTrait
      * @var Footprint|null The footprint of this part (e.g. DIP8)
      */
     #[Groups(['simple', 'extended', 'full', 'import'])]
-    #[ORM\ManyToOne(targetEntity: 'Footprint')]
+    #[ORM\ManyToOne(targetEntity: Footprint::class)]
     #[ORM\JoinColumn(name: 'id_footprint')]
     #[Selectable()]
     protected ?Footprint $footprint = null;
diff --git a/src/Entity/Parts/PartTraits/InstockTrait.php b/src/Entity/Parts/PartTraits/InstockTrait.php
index f4a95e16..23168fd3 100644
--- a/src/Entity/Parts/PartTraits/InstockTrait.php
+++ b/src/Entity/Parts/PartTraits/InstockTrait.php
@@ -40,7 +40,7 @@ trait InstockTrait
      */
     #[Assert\Valid]
     #[Groups(['extended', 'full', 'import'])]
-    #[ORM\OneToMany(targetEntity: 'PartLot', mappedBy: 'part', cascade: ['persist', 'remove'], orphanRemoval: true)]
+    #[ORM\OneToMany(targetEntity: PartLot::class, mappedBy: 'part', cascade: ['persist', 'remove'], orphanRemoval: true)]
     #[ORM\OrderBy(['amount' => 'DESC'])]
     protected Collection $partLots;
 
@@ -57,7 +57,7 @@ trait InstockTrait
      * @var ?MeasurementUnit the unit in which the part's amount is measured
      */
     #[Groups(['extended', 'full', 'import'])]
-    #[ORM\ManyToOne(targetEntity: 'MeasurementUnit')]
+    #[ORM\ManyToOne(targetEntity: MeasurementUnit::class)]
     #[ORM\JoinColumn(name: 'id_part_unit')]
     protected ?MeasurementUnit $partUnit = null;
 
diff --git a/src/Entity/Parts/PartTraits/ManufacturerTrait.php b/src/Entity/Parts/PartTraits/ManufacturerTrait.php
index 1aa3d988..81ab8ac9 100644
--- a/src/Entity/Parts/PartTraits/ManufacturerTrait.php
+++ b/src/Entity/Parts/PartTraits/ManufacturerTrait.php
@@ -39,7 +39,7 @@ trait ManufacturerTrait
      * @var Manufacturer|null The manufacturer of this part
      */
     #[Groups(['simple', 'extended', 'full', 'import'])]
-    #[ORM\ManyToOne(targetEntity: 'Manufacturer')]
+    #[ORM\ManyToOne(targetEntity: Manufacturer::class)]
     #[ORM\JoinColumn(name: 'id_manufacturer')]
     #[Selectable()]
     protected ?Manufacturer $manufacturer = null;
diff --git a/src/Entity/Parts/PartTraits/OrderTrait.php b/src/Entity/Parts/PartTraits/OrderTrait.php
index b17f014b..2e0ec0b2 100644
--- a/src/Entity/Parts/PartTraits/OrderTrait.php
+++ b/src/Entity/Parts/PartTraits/OrderTrait.php
@@ -98,7 +98,7 @@ trait OrderTrait
      *
      * @param bool $hide_obsolete If true, obsolete orderdetails will NOT be returned
      *
-     * @return Collection|Orderdetail[] * all orderdetails as a one-dimensional array of Orderdetails objects
+     * @return Collection<int, Orderdetail> * all orderdetails as a one-dimensional array of Orderdetails objects
      *                                  (empty array if there are no ones)
      *                                  * the array is sorted by the suppliers names / minimum order quantity
      */
diff --git a/src/Entity/Parts/Storelocation.php b/src/Entity/Parts/Storelocation.php
index 205735d4..08c4911b 100644
--- a/src/Entity/Parts/Storelocation.php
+++ b/src/Entity/Parts/Storelocation.php
@@ -45,18 +45,18 @@ use Symfony\Component\Validator\Constraints as Assert;
 #[ORM\Index(name: 'location_idx_parent_name', columns: ['parent_id', 'name'])]
 class Storelocation extends AbstractPartsContainingDBElement
 {
-    #[ORM\OneToMany(targetEntity: 'Storelocation', mappedBy: 'parent')]
+    #[ORM\OneToMany(targetEntity: self::class, mappedBy: 'parent')]
     #[ORM\OrderBy(['name' => 'ASC'])]
     protected Collection $children;
 
-    #[ORM\ManyToOne(targetEntity: 'Storelocation', inversedBy: 'children')]
+    #[ORM\ManyToOne(targetEntity: self::class, inversedBy: 'children')]
     #[ORM\JoinColumn(name: 'parent_id')]
     protected ?AbstractStructuralDBElement $parent = null;
 
     /**
      * @var MeasurementUnit|null The measurement unit, which parts can be stored in here
      */
-    #[ORM\ManyToOne(targetEntity: 'MeasurementUnit')]
+    #[ORM\ManyToOne(targetEntity: MeasurementUnit::class)]
     #[ORM\JoinColumn(name: 'storage_type_id')]
     protected ?MeasurementUnit $storage_type = null;
 
diff --git a/src/Entity/Parts/Supplier.php b/src/Entity/Parts/Supplier.php
index f7c56b2e..34483ca3 100644
--- a/src/Entity/Parts/Supplier.php
+++ b/src/Entity/Parts/Supplier.php
@@ -49,11 +49,11 @@ use Symfony\Component\Validator\Constraints as Assert;
 #[ORM\Index(name: 'supplier_idx_parent_name', columns: ['parent_id', 'name'])]
 class Supplier extends AbstractCompany
 {
-    #[ORM\OneToMany(targetEntity: 'Supplier', mappedBy: 'parent')]
+    #[ORM\OneToMany(targetEntity: self::class, mappedBy: 'parent')]
     #[ORM\OrderBy(['name' => 'ASC'])]
     protected Collection $children;
 
-    #[ORM\ManyToOne(targetEntity: 'Supplier', inversedBy: 'children')]
+    #[ORM\ManyToOne(targetEntity: self::class, inversedBy: 'children')]
     #[ORM\JoinColumn(name: 'parent_id')]
     protected ?AbstractStructuralDBElement $parent = null;
 
diff --git a/src/Entity/PriceInformations/Currency.php b/src/Entity/PriceInformations/Currency.php
index 171f5693..7e51c4c4 100644
--- a/src/Entity/PriceInformations/Currency.php
+++ b/src/Entity/PriceInformations/Currency.php
@@ -66,11 +66,11 @@ class Currency extends AbstractStructuralDBElement
     #[ORM\Column(type: Types::STRING)]
     protected string $iso_code = "";
 
-    #[ORM\OneToMany(targetEntity: 'Currency', mappedBy: 'parent', cascade: ['persist'])]
+    #[ORM\OneToMany(targetEntity: self::class, mappedBy: 'parent', cascade: ['persist'])]
     #[ORM\OrderBy(['name' => 'ASC'])]
     protected Collection $children;
 
-    #[ORM\ManyToOne(targetEntity: 'Currency', inversedBy: 'children')]
+    #[ORM\ManyToOne(targetEntity: self::class, inversedBy: 'children')]
     #[ORM\JoinColumn(name: 'parent_id')]
     protected ?AbstractStructuralDBElement $parent = null;
 
diff --git a/src/Entity/PriceInformations/Orderdetail.php b/src/Entity/PriceInformations/Orderdetail.php
index f39690d4..40d512a5 100644
--- a/src/Entity/PriceInformations/Orderdetail.php
+++ b/src/Entity/PriceInformations/Orderdetail.php
@@ -52,7 +52,7 @@ class Orderdetail extends AbstractDBElement implements TimeStampableInterface, N
 
     #[Assert\Valid]
     #[Groups(['extended', 'full', 'import'])]
-    #[ORM\OneToMany(targetEntity: 'Pricedetail', mappedBy: 'orderdetail', cascade: ['persist', 'remove'], orphanRemoval: true)]
+    #[ORM\OneToMany(targetEntity: Pricedetail::class, mappedBy: 'orderdetail', cascade: ['persist', 'remove'], orphanRemoval: true)]
     #[ORM\OrderBy(['min_discount_quantity' => 'ASC'])]
     protected Collection $pricedetails;
 
diff --git a/src/Entity/PriceInformations/Pricedetail.php b/src/Entity/PriceInformations/Pricedetail.php
index 34df9e57..26afbb50 100644
--- a/src/Entity/PriceInformations/Pricedetail.php
+++ b/src/Entity/PriceInformations/Pricedetail.php
@@ -64,7 +64,7 @@ class Pricedetail extends AbstractDBElement implements TimeStampableInterface
      *                If this is null, the global base unit is assumed
      */
     #[Groups(['extended', 'full', 'import'])]
-    #[ORM\ManyToOne(targetEntity: 'Currency', inversedBy: 'pricedetails')]
+    #[ORM\ManyToOne(targetEntity: Currency::class, inversedBy: 'pricedetails')]
     #[ORM\JoinColumn(name: 'id_currency')]
     #[Selectable()]
     protected ?Currency $currency = null;
@@ -95,7 +95,7 @@ class Pricedetail extends AbstractDBElement implements TimeStampableInterface
      * @var Orderdetail|null
      */
     #[Assert\NotNull]
-    #[ORM\ManyToOne(targetEntity: 'Orderdetail', inversedBy: 'pricedetails')]
+    #[ORM\ManyToOne(targetEntity: Orderdetail::class, inversedBy: 'pricedetails')]
     #[ORM\JoinColumn(name: 'orderdetails_id', nullable: false, onDelete: 'CASCADE')]
     protected ?Orderdetail $orderdetail = null;
 
diff --git a/src/Entity/ProjectSystem/Project.php b/src/Entity/ProjectSystem/Project.php
index 966d19c1..0b07ef22 100644
--- a/src/Entity/ProjectSystem/Project.php
+++ b/src/Entity/ProjectSystem/Project.php
@@ -45,17 +45,17 @@ use Symfony\Component\Validator\Context\ExecutionContextInterface;
 #[ORM\Table(name: 'projects')]
 class Project extends AbstractStructuralDBElement
 {
-    #[ORM\OneToMany(targetEntity: 'Project', mappedBy: 'parent')]
+    #[ORM\OneToMany(targetEntity: self::class, mappedBy: 'parent')]
     #[ORM\OrderBy(['name' => 'ASC'])]
     protected Collection $children;
 
-    #[ORM\ManyToOne(targetEntity: 'Project', inversedBy: 'children')]
+    #[ORM\ManyToOne(targetEntity: self::class, inversedBy: 'children')]
     #[ORM\JoinColumn(name: 'parent_id')]
     protected ?AbstractStructuralDBElement $parent = null;
 
     #[Assert\Valid]
     #[Groups(['extended', 'full'])]
-    #[ORM\OneToMany(targetEntity: 'ProjectBOMEntry', mappedBy: 'project', cascade: ['persist', 'remove'], orphanRemoval: true)]
+    #[ORM\OneToMany(targetEntity: ProjectBOMEntry::class, mappedBy: 'project', cascade: ['persist', 'remove'], orphanRemoval: true)]
     protected Collection $bom_entries;
 
     #[ORM\Column(type: Types::INTEGER)]
diff --git a/src/Entity/ProjectSystem/ProjectBOMEntry.php b/src/Entity/ProjectSystem/ProjectBOMEntry.php
index 4469f86f..af8b48c1 100644
--- a/src/Entity/ProjectSystem/ProjectBOMEntry.php
+++ b/src/Entity/ProjectSystem/ProjectBOMEntry.php
@@ -76,7 +76,7 @@ class ProjectBOMEntry extends AbstractDBElement
     /**
      * @var Project|null
      */
-    #[ORM\ManyToOne(targetEntity: 'Project', inversedBy: 'bom_entries')]
+    #[ORM\ManyToOne(targetEntity: Project::class, inversedBy: 'bom_entries')]
     #[ORM\JoinColumn(name: 'id_device')]
     protected ?Project $project = null;
 
diff --git a/src/Entity/UserSystem/Group.php b/src/Entity/UserSystem/Group.php
index f833fdfc..b56cabf4 100644
--- a/src/Entity/UserSystem/Group.php
+++ b/src/Entity/UserSystem/Group.php
@@ -47,18 +47,18 @@ use Symfony\Component\Validator\Constraints as Assert;
 #[NoLockout()]
 class Group extends AbstractStructuralDBElement implements HasPermissionsInterface
 {
-    #[ORM\OneToMany(targetEntity: 'Group', mappedBy: 'parent')]
+    #[ORM\OneToMany(targetEntity: self::class, mappedBy: 'parent')]
     #[ORM\OrderBy(['name' => 'ASC'])]
     protected Collection $children;
 
-    #[ORM\ManyToOne(targetEntity: 'Group', inversedBy: 'children')]
+    #[ORM\ManyToOne(targetEntity: self::class, inversedBy: 'children')]
     #[ORM\JoinColumn(name: 'parent_id')]
     protected ?AbstractStructuralDBElement $parent = null;
 
     /**
      * @var Collection<int, User>
      */
-    #[ORM\OneToMany(targetEntity: 'User', mappedBy: 'group')]
+    #[ORM\OneToMany(targetEntity: User::class, mappedBy: 'group')]
     protected Collection $users;
 
     /**
@@ -77,7 +77,7 @@ class Group extends AbstractStructuralDBElement implements HasPermissionsInterfa
     protected Collection $attachments;
 
     #[Groups(['full'])]
-    #[ORM\Embedded(class: 'PermissionData', columnPrefix: 'permissions_')]
+    #[ORM\Embedded(class: PermissionData::class, columnPrefix: 'permissions_')]
     #[ValidPermission()]
     protected ?PermissionData $permissions = null;
 
diff --git a/src/Entity/UserSystem/User.php b/src/Entity/UserSystem/User.php
index 614f01e5..da6a240f 100644
--- a/src/Entity/UserSystem/User.php
+++ b/src/Entity/UserSystem/User.php
@@ -133,7 +133,7 @@ class User extends AttachmentContainingDBElement implements UserInterface, HasPe
      * DO NOT PUT A fetch eager here! Otherwise, you can not unset the group of a user! This seems to be some kind of bug in doctrine. Maybe this is fixed in future versions.
      */
     #[Groups(['extended', 'full', 'import'])]
-    #[ORM\ManyToOne(targetEntity: 'Group', inversedBy: 'users')]
+    #[ORM\ManyToOne(targetEntity: Group::class, inversedBy: 'users')]
     #[ORM\JoinColumn(name: 'group_id')]
     #[Selectable]
     protected ?Group $group = null;
diff --git a/src/EventSubscriber/UserSystem/UpgradePermissionsSchemaSubscriber.php b/src/EventSubscriber/UserSystem/UpgradePermissionsSchemaSubscriber.php
index 6e81ec85..613bc6ec 100644
--- a/src/EventSubscriber/UserSystem/UpgradePermissionsSchemaSubscriber.php
+++ b/src/EventSubscriber/UserSystem/UpgradePermissionsSchemaSubscriber.php
@@ -58,6 +58,11 @@ class UpgradePermissionsSchemaSubscriber implements EventSubscriberInterface
         $session = $event->getRequest()->getSession();
         $flashBag = $session->getFlashBag();
 
+        //Check if the user is an instance of User, otherwise we can't upgrade the schema
+        if (!$user instanceof User) {
+            return;
+        }
+
         if ($this->permissionSchemaUpdater->isSchemaUpdateNeeded($user)) {
             $this->eventCommentHelper->setMessage('Automatic permission schema update');
             $this->permissionSchemaUpdater->userUpgradeSchemaRecursively($user);
diff --git a/src/Repository/LogEntryRepository.php b/src/Repository/LogEntryRepository.php
index a3456b6c..770e6cd6 100644
--- a/src/Repository/LogEntryRepository.php
+++ b/src/Repository/LogEntryRepository.php
@@ -52,13 +52,13 @@ class LogEntryRepository extends DBElementRepository
      * Find log entries associated with the given element (the history of the element).
      *
      * @param AbstractDBElement $element The element for which the history should be generated
-     * @param  string  $order   By default, the newest entries are shown first. Change this to ASC to show the oldest entries first.
-     * @param null              $limit
-     * @param null              $offset
+     * @param string  $order   By default, the newest entries are shown first. Change this to ASC to show the oldest entries first.
+     * @param int|null              $limit
+     * @param int|null              $offset
      *
      * @return AbstractLogEntry[]
      */
-    public function getElementHistory(AbstractDBElement $element, string $order = 'DESC', $limit = null, $offset = null): array
+    public function getElementHistory(AbstractDBElement $element, string $order = 'DESC', ?int $limit = null, ?int $offset = null): array
     {
         return $this->findBy(['element' => $element], ['timestamp' => $order], $limit, $offset);
     }
@@ -100,11 +100,11 @@ class LogEntryRepository extends DBElementRepository
      * Gets all log entries that are related to time travelling.
      *
      * @param AbstractDBElement $element The element for which the time travel data should be retrieved
-     * @param DateTime         $until   Back to which timestamp should the data be got (including the timestamp)
+     * @param \DateTimeInterface $until   Back to which timestamp should the data be got (including the timestamp)
      *
      * @return AbstractLogEntry[]
      */
-    public function getTimetravelDataForElement(AbstractDBElement $element, DateTime $until): array
+    public function getTimetravelDataForElement(AbstractDBElement $element, \DateTimeInterface $until): array
     {
         $qb = $this->createQueryBuilder('log');
         $qb->select('log')
@@ -132,7 +132,7 @@ class LogEntryRepository extends DBElementRepository
      *
      * @return bool True if the element existed at the given timestamp
      */
-    public function getElementExistedAtTimestamp(AbstractDBElement $element, DateTime $timestamp): bool
+    public function getElementExistedAtTimestamp(AbstractDBElement $element, \DateTimeInterface $timestamp): bool
     {
         $qb = $this->createQueryBuilder('log');
         $qb->select('count(log)')
@@ -157,8 +157,8 @@ class LogEntryRepository extends DBElementRepository
     /**
      * Gets the last log entries ordered by timestamp.
      *
-     * @param null   $limit
-     * @param null   $offset
+     * @param int|null   $limit
+     * @param int|null   $offset
      */
     public function getLogsOrderedByTimestamp(string $order = 'DESC', $limit = null, $offset = null): array
     {
diff --git a/src/Services/ElementTypeNameGenerator.php b/src/Services/ElementTypeNameGenerator.php
index e9b24d23..f907712b 100644
--- a/src/Services/ElementTypeNameGenerator.php
+++ b/src/Services/ElementTypeNameGenerator.php
@@ -26,6 +26,7 @@ use App\Entity\Attachments\AttachmentContainingDBElement;
 use App\Entity\Attachments\Attachment;
 use App\Entity\Attachments\AttachmentType;
 use App\Entity\Base\AbstractDBElement;
+use App\Entity\Base\AbstractNamedDBElement;
 use App\Entity\Contracts\NamedElementInterface;
 use App\Entity\ProjectSystem\Project;
 use App\Entity\LabelSystem\LabelProfile;
@@ -180,7 +181,7 @@ class ElementTypeNameGenerator
                 $on = $entity->getProject();
             }
 
-            if (isset($on) && is_object($on)) {
+            if (isset($on) && $on instanceof NamedElementInterface) {
                 try {
                     $tmp .= sprintf(
                         ' (<a href="%s">%s</a>)',
diff --git a/src/Services/LabelSystem/LabelExampleElementsGenerator.php b/src/Services/LabelSystem/LabelExampleElementsGenerator.php
index 40ebafa0..a5e194b2 100644
--- a/src/Services/LabelSystem/LabelExampleElementsGenerator.php
+++ b/src/Services/LabelSystem/LabelExampleElementsGenerator.php
@@ -132,6 +132,14 @@ final class LabelExampleElementsGenerator
         return $user;
     }
 
+    /**
+     * @template T of AbstractStructuralDBElement
+     * @param  string  $class
+     * @phpstan-param class-string<T> $class
+     * @return AbstractStructuralDBElement
+     * @phpstan-return T
+     * @throws \ReflectionException
+     */
     private function getStructuralData(string $class): AbstractStructuralDBElement
     {
         if (!is_a($class, AbstractStructuralDBElement::class, true)) {
diff --git a/src/Services/LabelSystem/PlaceholderProviders/BarcodeProvider.php b/src/Services/LabelSystem/PlaceholderProviders/BarcodeProvider.php
index eb413518..11824054 100644
--- a/src/Services/LabelSystem/PlaceholderProviders/BarcodeProvider.php
+++ b/src/Services/LabelSystem/PlaceholderProviders/BarcodeProvider.php
@@ -22,6 +22,7 @@ declare(strict_types=1);
  */
 namespace App\Services\LabelSystem\PlaceholderProviders;
 
+use App\Entity\LabelSystem\BarcodeType;
 use App\Entity\LabelSystem\LabelOptions;
 use App\Services\LabelSystem\BarcodeGenerator;
 use App\Services\LabelSystem\Barcodes\BarcodeContentGenerator;
@@ -52,19 +53,19 @@ final class BarcodeProvider implements PlaceholderProviderInterface
 
         if ('[[BARCODE_QR]]' === $placeholder) {
             $label_options = new LabelOptions();
-            $label_options->setBarcodeType('qr');
+            $label_options->setBarcodeType(BarcodeType::QR);
             return $this->barcodeGenerator->generateHTMLBarcode($label_options, $label_target);
         }
 
         if ('[[BARCODE_C39]]' === $placeholder) {
             $label_options = new LabelOptions();
-            $label_options->setBarcodeType('code39');
+            $label_options->setBarcodeType(BarcodeType::CODE39);
             return $this->barcodeGenerator->generateHTMLBarcode($label_options, $label_target);
         }
 
         if ('[[BARCODE_C128]]' === $placeholder) {
             $label_options = new LabelOptions();
-            $label_options->setBarcodeType('code128');
+            $label_options->setBarcodeType(BarcodeType::CODE128);
             return $this->barcodeGenerator->generateHTMLBarcode($label_options, $label_target);
         }
 
diff --git a/src/Services/LogSystem/TimeTravel.php b/src/Services/LogSystem/TimeTravel.php
index 5cc4be79..82e98afb 100644
--- a/src/Services/LogSystem/TimeTravel.php
+++ b/src/Services/LogSystem/TimeTravel.php
@@ -79,7 +79,7 @@ class TimeTravel
      *
      * @throws Exception
      */
-    public function revertEntityToTimestamp(AbstractDBElement $element, DateTime $timestamp, array $reverted_elements = []): void
+    public function revertEntityToTimestamp(AbstractDBElement $element, \DateTimeInterface $timestamp, array $reverted_elements = []): void
     {
         if (!$element instanceof TimeStampableInterface) {
             throw new InvalidArgumentException('$element must have a Timestamp!');
@@ -228,7 +228,7 @@ class TimeTravel
         $this->setField($element, 'lastModified', $logEntry->getTimestamp());
     }
 
-    protected function getField(AbstractDBElement $element, string $field)
+    protected function getField(AbstractDBElement $element, string $field): mixed
     {
         $reflection = new ReflectionClass($element::class);
         $property = $reflection->getProperty($field);
@@ -237,7 +237,7 @@ class TimeTravel
         return $property->getValue($element);
     }
 
-    protected function setField(AbstractDBElement $element, string $field, \DateTime|int|null $new_value): void
+    protected function setField(AbstractDBElement $element, string $field, mixed $new_value): void
     {
         $reflection = new ReflectionClass($element::class);
         $property = $reflection->getProperty($field);
diff --git a/src/Services/UserSystem/PermissionManager.php b/src/Services/UserSystem/PermissionManager.php
index 333e6168..fa591a91 100644
--- a/src/Services/UserSystem/PermissionManager.php
+++ b/src/Services/UserSystem/PermissionManager.php
@@ -112,7 +112,7 @@ class PermissionManager
 
         /** @var Group $parent */
         $parent = $user->getGroup();
-        while ($parent instanceof AbstractStructuralDBElement) { //The top group, has parent == null
+        while ($parent instanceof Group) { //The top group, has parent == null
             //Check if our current element gives an info about disallow/allow
             $allowed = $this->dontInherit($parent, $permission, $operation);
             if (null !== $allowed) {
diff --git a/src/Services/UserSystem/PermissionPresetsHelper.php b/src/Services/UserSystem/PermissionPresetsHelper.php
index d12eb1ef..ecc56699 100644
--- a/src/Services/UserSystem/PermissionPresetsHelper.php
+++ b/src/Services/UserSystem/PermissionPresetsHelper.php
@@ -172,12 +172,18 @@ class PermissionPresetsHelper
         return $perm_holder;
     }
 
+    /**
+     * @phpstan-api
+     */
     private function AllForbid(HasPermissionsInterface $perm_holder): HasPermissionsInterface
     {
         $this->permissionResolver->setAllPermissions($perm_holder, PermissionData::DISALLOW);
         return $perm_holder;
     }
 
+    /**
+     * @phpstan-api
+     */
     private function AllAllow(HasPermissionsInterface $perm_holder): HasPermissionsInterface
     {
         $this->permissionResolver->setAllPermissions($perm_holder, PermissionData::ALLOW);