of corse it was a user problem 
Now I remember: After installing Zorin 18 I realized, that custom keyboard shortcuts didn't work with flameshot and I found a solution, where someone wrote that you can switch back to X11 and everything works fine.
Thats the reason why I switched back- and maybe the reason for this problems and maybe some other problems like this Dynamic taskbar returning back to static after some time too 
Now I found another solution to solve the screenshot problem Flameshot Print Button not working on Zorin 18 - Solution and will stay on wayland. maybe this solves this problem, I'll have an eye on that 
Thank you all very much for your help!