Thank you for your help. You are right, the "@" was wrong, but even now it's not working.
Here are my settings. Maybe you can find the mistake.
These are the DNS Settings for my Domain in Plesk (my Domain name is http://example.studio/)
And these are my DNS settings at my domain provider...
I know this is a very popular topic and very often discussed. I checked almost every forum and thread to get it right, but somehow it's not working.
First off I own a Domain on namecheap and a linux server at hetzner with Plesk 12.5.30 installed on it.
I enabled following settings in Plesk...