my friends cant hear me when i play games

basicaly when i play any game (league of legends , minecraft or just any) my ping is normal in the game but for some reason i cant hear or speak to my friends while playing.

also i have realised that when i go back to discord (alt+tab) , discord pops up as if it was minimized AND..

i think that this is the problem (because when you minimize an app or browser it will use less data than it actualy should).

this is my only clues but i dont know how to fix it ;(

also my computer is bad to meeh so if thats also a reason please someone tell me :)

thanks for you timez