Hey thanks for your answer. ??
Everything was working fine for the last 2 months. I updated a few plugins (ACF, Wordfence, Duplicate Post, Yoast and optimole) and cleared the cache afterwards (Autoptimize)
The website was working for a few hours and then i got Mail from my Uptime Robot that the website sends HTTP 500 Error.
The last change on the website was some Analytics code and i deleted 2 Users. Thats all. ??