Fatal error: Uncaught Error: Interface "Psr\Http\Server\RequestHandlerInterface" not found in /var/www/html/dev.hallescherfc.de/vendor/typo3/cms-backend/Classes/Http/RequestHandler.php:42 Stack trace: #0 {main} thrown in /var/www/html/dev.hallescherfc.de/vendor/typo3/cms-backend/Classes/Http/RequestHandler.php on line 42