Screen randomly freezing

Any idea how to diagnose this,I have no idea from where to even begin

I have a laptop connected to a monitor which(the laptop supports 240hz(2560x1600)and the monitor 60hz...and up to 1920x1080p)
The project mode is set to make only the monitor active(second screen only)
Randomly for some reason,everything just kinda freezes.
For example nothing is updated on the screen(except the mouse,for some reason there is no problem with it at all,all mouse movements are displayed correctly),when I try to minimize a window,this happens after maybe 5 seconds,when I press the windows key,the start menu appears after around 5 seconds
Ctrl+Alt+Delete the screen appears after 5 seconds
It's not high gpu/cpu load,I will hears the fans if it was that and I have

When I switch the projector(Windows key+P)to the laptop screen only and everything start working and when I switch to the monitor only again,the problem is fixed for I don't know how long

Do you have it in extended mode (laptop + monitor) or just monitor? I would run it in extended if not already and see if the issue is only on the monitor. You could also trying running at a lower refresh rate and see if the freezing subsides.

The smoothness of motion that the human eye can detect is called the "flicker fusion threshold" and for more people 90Hz+ is the point at which the human eye doesn't detect any difference