Everytime I decreased my visual setting it maximizes the whole settings at every restarts. I dont know if I used a console command unintentionally. How can I solve this?
Installing CSGO with custom HUDs will preload the conditions of the hud everytime you run the game. Some HUDs are more demanding than others, and will amp up your graphics everytime you run it, while some are less demanding.
Just uninstall your HUD, and you should be fine. If you don't know how to uninstall your HUD, an easier fix is to go to the Game Properties option by right-clicking the game in Steam, then click Validate Game Files. This will check for discrepancies in your game client and the actual game, and reset your settings accordingly.