=> download vibranceGUI ( https://vibrancegui.com/ )
=> put "-windowed -noborder" in your cs2 launch options
- if still in fullscreen, put "windowed" in video settings and put to your desired stretched resolution
=> go into vibranceGUI
=> add cs2
=> double click on cs2 icon
=> check the box for "change resolution when ingame"
=> change the resolution to your desired stretched resolution, not your native resolution and save
=> restart game

example: native for me is 3440x1440 so i put game to 2560x1440 and change vibrancegui ingame res to "2560x1440 @144hz (32 bit, Stretch)"