Sorry the url was misformed in my inital post: https://<url>/settings/admin/serverinfo. Just go to your admin settings and to system. Have look if it actually shows PHP 8.0 (and not PHP 7.4 or something).
Just noticed you already opened a thread about this: Fehler: Die PHP-Speichergrenze liegt unterhalb des empfohlenen Wertes von 512MB
Please keep it in one thread, it just makes it harder for every one to help you.