diff --git a/.github/CONTRIBUTING.md b/.github/CONTRIBUTING.md
index 002547ccedd..8dca798b0b6 100755
--- a/.github/CONTRIBUTING.md
+++ b/.github/CONTRIBUTING.md
@@ -13,12 +13,12 @@ email, or any other method with the owners of this repository before making a ch
 ## Making Changes
 
 * Create a topic branch from where you want to base your work.
-  * This is usually the master branch.
+  * This is usually the main branch.
   * Only target release branches if you are certain your fix must be on that
     branch.
-  * To quickly create a topic branch based on master; `git checkout -b
-    fix/master/my_contribution master`. Please avoid working directly on the
-    `master` branch.
+  * To quickly create a topic branch based on main; `git checkout -b
+    fix/main/my_contribution main`. Please avoid working directly on the
+    `main` branch.
 * Make commits of logical units.
 * Make sure your commit messages are in the proper format. Use either `[TASK]`, `[FEATURE]`, `[BUGFIX]` or `[DOC]`
 
@@ -41,5 +41,5 @@ For changes of a trivial nature, it is not always necessary to create a new issu
 
 ## Additional resources
 
-* [Documentation](https://github.com/lochmueller/staticfilecache/tree/master/Documentation)
+* [Documentation](https://github.com/lochmueller/staticfilecache/tree/main/Documentation)
 * [How to Write a Git Commit Message](http://chris.beams.io/posts/git-commit/)
diff --git a/Classes/Cache/StaticDatabaseBackend.php b/Classes/Cache/StaticDatabaseBackend.php
index 36002aef2d2..1064a63bc30 100644
--- a/Classes/Cache/StaticDatabaseBackend.php
+++ b/Classes/Cache/StaticDatabaseBackend.php
@@ -74,10 +74,8 @@ public function getTableDefinitions()
 
     /**
      * Get the real life time.
-     *
-     * @param int $lifetime
      */
-    protected function getRealLifetime($lifetime): int
+    protected function getRealLifetime(?int $lifetime): int
     {
         if (null === $lifetime) {
             $lifetime = $this->defaultLifetime;
diff --git a/Classes/Cache/StaticFileBackend.php b/Classes/Cache/StaticFileBackend.php
index 549eaf93720..591876d0abf 100644
--- a/Classes/Cache/StaticFileBackend.php
+++ b/Classes/Cache/StaticFileBackend.php
@@ -45,7 +45,7 @@ public function __construct($context, array $options = [])
      * Saves data in the cache.
      *
      * @param string $entryIdentifier An identifier for this specific cache entry
-     * @param ResponseInterface $data The data to be stored
+     * @param string $data The data to be stored
      * @param array $tags Tags to associate with this cache entry
      * @param int $lifetime Lifetime of this cache entry in seconds
      *
@@ -54,6 +54,7 @@ public function __construct($context, array $options = [])
      */
     public function set($entryIdentifier, $data, array $tags = [], $lifetime = null): void
     {
+        /** @var ResponseInterface $data */
         $realLifetime = $this->getRealLifetime($lifetime);
         $time = (new DateTimeService())->getCurrentTime();
         $databaseData = [
diff --git a/Classes/Controller/BackendController.php b/Classes/Controller/BackendController.php
index 45ef1b8281d..f2e8cbc0d73 100644
--- a/Classes/Controller/BackendController.php
+++ b/Classes/Controller/BackendController.php
@@ -6,6 +6,7 @@
 
 use Psr\Log\LoggerAwareInterface;
 use Psr\Log\LoggerAwareTrait;
+use SFC\Staticfilecache\Cache\UriFrontend;
 use TYPO3\CMS\Backend\Template\Components\Menu\Menu;
 use TYPO3\CMS\Backend\Template\Components\Menu\MenuItem;
 use TYPO3\CMS\Core\Type\ContextualFeedbackSeverity;
@@ -33,7 +34,8 @@ class BackendController extends ActionController implements LoggerAwareInterface
     public function __construct(
         readonly protected QueueService          $queueService,
         readonly protected ModuleTemplateFactory $moduleTemplateFactory,
-        readonly protected ConfigurationService  $configurationService
+        readonly protected ConfigurationService  $configurationService,
+        readonly protected CacheService          $cacheService,
     ) {}
 
     public function listAction(string $filter = ''): ResponseInterface
@@ -124,7 +126,8 @@ protected function getCachePagesEntries(string $filter): array
         $rows = [];
 
         try {
-            $cache = GeneralUtility::makeInstance(CacheService::class)->get();
+            /** @var UriFrontend $cache */
+            $cache = $this->cacheService->get();
         } catch (\Exception $exception) {
             $this->logger->error('Problems by fetching the cache: ' . $exception->getMessage() . ' / ' . $exception->getFile() . ':' . $exception->getLine());
 
diff --git a/Classes/Domain/Repository/QueueRepository.php b/Classes/Domain/Repository/QueueRepository.php
index 0722aba2d9e..775a41ae108 100644
--- a/Classes/Domain/Repository/QueueRepository.php
+++ b/Classes/Domain/Repository/QueueRepository.php
@@ -45,7 +45,7 @@ public function countOpenByIdentifier($identifier): int
 
     /**
      * Find old entries.
-     * @return iterable<int>
+     * @return iterable<array{uid: int}>
      */
     public function findOldUids(): iterable
     {
diff --git a/Classes/Middleware/GenerateMiddleware.php b/Classes/Middleware/GenerateMiddleware.php
index bfe2cbb8221..744243c05d4 100644
--- a/Classes/Middleware/GenerateMiddleware.php
+++ b/Classes/Middleware/GenerateMiddleware.php
@@ -4,6 +4,7 @@
 
 namespace SFC\Staticfilecache\Middleware;
 
+use TYPO3\CMS\Core\Cache\Frontend\FrontendInterface;
 use TYPO3\CMS\Core\Context\Context;
 use Psr\EventDispatcher\EventDispatcherInterface;
 use Psr\Http\Message\ResponseInterface;
@@ -24,13 +25,14 @@
 
 class GenerateMiddleware implements MiddlewareInterface
 {
-    protected ?UriFrontend $cache = null;
+    protected ?FrontendInterface $cache = null;
     protected ServerRequestInterface $request;
 
     public function __construct(
         readonly protected EventDispatcherInterface $eventDispatcher,
         readonly protected CookieService $cookieService,
-        readonly protected Typo3Version $typo3Version
+        readonly protected Typo3Version $typo3Version,
+        readonly protected CacheService $cacheService
     ) {}
 
     /**
@@ -54,7 +56,7 @@ public function process(ServerRequestInterface $request, RequestHandlerInterface
         }
 
         try {
-            $this->cache = GeneralUtility::makeInstance(CacheService::class)->get();
+            $this->cache = $this->cacheService->get();
         } catch (\Exception $exception) {
             return $this->removeSfcHeaders($response);
         }
diff --git a/Classes/Service/CacheService.php b/Classes/Service/CacheService.php
index 8e713fc703f..b9013b92d7e 100644
--- a/Classes/Service/CacheService.php
+++ b/Classes/Service/CacheService.php
@@ -9,6 +9,7 @@
 use SFC\Staticfilecache\Domain\Repository\QueueRepository;
 use TYPO3\CMS\Core\Cache\CacheManager;
 use TYPO3\CMS\Core\Cache\Exception\NoSuchCacheException;
+use TYPO3\CMS\Core\Cache\Frontend\FrontendInterface;
 use TYPO3\CMS\Core\Cache\Frontend\VariableFrontend;
 use TYPO3\CMS\Core\Core\Environment;
 use TYPO3\CMS\Core\Utility\GeneralUtility;
@@ -20,7 +21,7 @@ class CacheService
      *
      * @throws NoSuchCacheException
      */
-    public function get(): UriFrontend
+    public function get(): FrontendInterface
     {
         return $this->getManager()->getCache('staticfilecache');
     }
diff --git a/Classes/Service/ClientService.php b/Classes/Service/ClientService.php
index 9d2f584f780..720f8f4f65a 100644
--- a/Classes/Service/ClientService.php
+++ b/Classes/Service/ClientService.php
@@ -76,7 +76,7 @@ protected function getCallableClient(string $domain): Client
         $httpOptions['verify'] = filter_var($httpOptions['verify'], FILTER_VALIDATE_BOOLEAN, FILTER_NULL_ON_FAILURE) ?? $httpOptions['verify'];
         if (isset($httpOptions['handler']) && \is_array($httpOptions['handler'])) {
             $stack = HandlerStack::create();
-            foreach ($httpOptions['handler'] ?? [] as $handler) {
+            foreach ($httpOptions['handler'] as $handler) {
                 $stack->push($handler);
             }
             $httpOptions['handler'] = $stack;
diff --git a/Classes/Service/InlineAssets/InlineFavIcon.php b/Classes/Service/InlineAssets/InlineFavIcon.php
index b822364a13d..76d38850d6a 100644
--- a/Classes/Service/InlineAssets/InlineFavIcon.php
+++ b/Classes/Service/InlineAssets/InlineFavIcon.php
@@ -14,7 +14,7 @@ class InlineFavIcon extends AbstractInlineAssets
     /**
      * FavIcon extensions.
      */
-    private $favIconExtensions = ['svg', 'ico', 'png'];
+    private array $favIconExtensions = ['svg', 'ico', 'png'];
 
     /**
      * Check if the class can handle the file extension.
diff --git a/Classes/Service/InlineAssets/InlineImages.php b/Classes/Service/InlineAssets/InlineImages.php
index 7d3bc1f216e..2294942fd18 100644
--- a/Classes/Service/InlineAssets/InlineImages.php
+++ b/Classes/Service/InlineAssets/InlineImages.php
@@ -14,7 +14,7 @@ class InlineImages extends AbstractInlineAssets
     /**
      * Image extensions.
      */
-    private $imageExtensions = ['png', 'jpg', 'jpeg'];
+    private array $imageExtensions = ['png', 'jpg', 'jpeg'];
 
     /**
      * Check if the class can handle the file extension.
diff --git a/Classes/Service/InlineAssets/InlineStyles.php b/Classes/Service/InlineAssets/InlineStyles.php
index 16e35097d3f..f472dff1f22 100644
--- a/Classes/Service/InlineAssets/InlineStyles.php
+++ b/Classes/Service/InlineAssets/InlineStyles.php
@@ -14,12 +14,12 @@ class InlineStyles extends AbstractInlineAssets
     /**
      * Image extensions.
      */
-    private $imageExtensions = ['ico', 'png', 'jpg', 'jpeg'];
+    private array $imageExtensions = ['ico', 'png', 'jpg', 'jpeg'];
 
     /**
      * Font extensions.
      */
-    private $fontExtensions = ['woff', 'woff2'];
+    private array $fontExtensions = ['woff', 'woff2'];
 
     /**
      * Check if the class can handle the file extension.
diff --git a/phpstan.neon b/phpstan.neon
index 504925c990f..7f692f5f0ee 100644
--- a/phpstan.neon
+++ b/phpstan.neon
@@ -3,5 +3,5 @@ includes:
 	- .Build/vendor/andersundsehr/phpstan-git-files/extension.php
 
 parameters:
-	level: 2
+	level: 5
 	reportUnmatchedIgnoredErrors: false