Hi,
I just want to let you know what I did as a little workaround regarding this issue:
I downloaded the mini-app “text command” into my taskbar and set the command xrandr --output DP-1 --mode 1920x1080 --rate 60 to it. So now everytime I switch to my second monitor, I then hit this button and can work with a clear screen.
And I want to thank you for all your time and help.