I did like you said and deactivated everything. And aso you allready assumed, it worked perfectly. After that I startet to activated the theme and the plugins one after the other. The theme was not the problem. As soon I activated the Autoptimize Plugin I got the error. So I’ll probably just leave it deactivated, it’s not a super critical plugin. As soon as a new version is available, I’ll try to activate it again.