One of the most common complaints by users when playing CS:GO is the fact that alt tabbing or minimizing the game to the desktop is slow or laggy or just takes an extremely long time. However there is no need to worry as there is now a confirmed fix which most users that are running Windows 10 are having success with.
The key is to turn off the feature in Windows 10 called ‘focus assist‘, and ‘When I’m playing a game‘ to OFF. The easiest way to find this setting is to just open your start menu and search for ‘focus assist settings’ and it should pop up, once you are in there, on the bottom you want to look for Automatic rules section and turn the selector to OFF for ‘When I’m playing a game’. Once doing this, restart or re-open CS:GO and try to minimize once in a game, you should notice a huge improvement as most users said it has reduced the time it takes from 5-10 seconds to just a half second or so.
For more information regarding this fix or to see what others are saying, check out the reddit thread.