Cannot change links of the design tab


I just installed the latest version of Nextcloud. Under the design tab in the damin area I cannot change the web link, the legal notice link or the privacy policy link. If I type in anything or try to make a change to the default web link, the loding icon appears but nothing happens after that. If I reload the page, nothing changed.

Is there any way to get around that?

Thanks in advance!

Linux 4.18.0-372.9.1.lve.el7h.x86_64 x86_64
PHP 7.4.29
Oracle MysSQL 5.7.36
Hosted Webspace

I contacted the hoster and they said, that they do not plan do update MySQL to version 8. I have limited understanding of how databases work, but seeing that nextcloud recommends version 8 my guess would be that this could be the source of the problem.