Dear Damien,
could your send the screenshots for these operations, how to complete these steps, because my informatics IQ is LOW
!
Many thanks
2) Open a terminal window: Select Finder > Go > Utilities > Terminal
3) Type in the following command to remove the user-specific configuration file for the currently logged in user:
3a) rm ~/Library/Preferences/com.apple.windowserver.*.plist
4) Type in the following command to remove the system-wide configuration file (requires root/administrative permissions):
4a) sudo rm /Library/Preferences/com.apple.windowserver.*.plist