This is a server issue. It is likely that your hosting / server is very limited with the amount of RAM that it has. You may want to consider looking for a better place to host your site.

In short, you need more RAM for your server / web host. You may want to try upgrading your host provider.

The statement is somewhat inaccurate but the concept is right. The issue is that your host is limiting how much memory your php scripts can use, however this doesn't mean that they don't have memory available but rather they are being restrictive with it. I imagine that whoever you are hosted with would happily modify your memory allowed limit if you sent them this error. If they give a fuss though it definitely is their issue and not yours so it may be time to look elsewhere.

or maybe you can even change that yourself in your php.ini

Many thanks for the information! I will contact the support. My host is in principle a very good one (hetzner), so i think they will help.
Best regards,
Andi

Many thanks for the information! I will contact the support. My host is in principle a very good one (hetzner), so i think they will help.
Best regards,
Andi