you'll probably need the in-game console to use some advanced commands.
If you've enabled the console, skip to the next step.
There are two methods to enable the in-game console:
Open Steam in your Computer
Right-Click on CS:GO and choose Properties
In GENERAL Tab, Open SET LAUNCH OPTION.
write "-console" without quotation and press ok.
Now You'll see the console whenever you open the game
You can also enable from the game's option menu
Just do like the picture below :
Now you can open the console with ~ button (above the Tab button):
Using the Console
After joining a match, Open up console and write :
And Press Enter.
The game will show you a message that players' voices are muted :