I didn't really fix that issue, but when I comment out the line with feh and add run variety & at the end. It works completely fine. There is still the Desktopverwaltung ist nicht aktiv message when I try to open the desktop settings. But as long as I don't use them everything works fine.
So if you have the same issue: download variety and add run variety & to ~/.config/qtile/scripts/autostart.sh