Hi Submate Welcome to Subsim check this link out Sir also I have Nvidia Control Panel Software installed on my Desktop Rig if you have a AMD GPU you must have similar software.
https://www.subsim.com/radioroom/sho...94&postcount=4
set your screen Resolution through your Gpu not just clicking on your desktop then clicking on display settngs
link below for driver updates if you have a AMD GPU you must have a AMD GPU Control Panel if so click on full screen mode then click apply job done.
https://www.amd.com/en/support
Hope this Helps.