This app will provide you a switch that allows only your main screen to work during csgo's sessions (to save fps) and that will extends screens where you close the game.
To install this app you just need to download the repo (or clone), then open 1_SwitchScreen.vbs
This will copy the .vbs and the .bat to the startup program's folder, so that will work every time that you launch your game!
after installing the VBS you can delete the files from the download's folder
To disable it you have open the Taskmanager (ctrl + alt + del then Taskmanager)
In the Startup tab, right click on 1_SwitchScreen.vbs and 2_SwitchScreen.bat and disable them, then reboot
To uninstall the app you have to delete it from startup program's folder
To do it press windows + R and write shell:startup
Delete 1_SwitchScreen.vbs and 2_SwitchScreen.bat then reboot
You can also disable it in the task Manager, startup tab
This script switch the display to the 1st screen only when you launch Cs2; type "/external" instead of "/internal" if the internal monitor is not wich one you need line 33 in the 2_SwitchScreen.bat file then reinstall the programm