maybe he is using a higher resolution than you, and also check his video settings on csgo vs yours
Too little peace of information, maybe your friend just a lamer.
Things I would check if I found myself in this situation: thermals, then video config (check if multicore rendering is turned off), then check for any background processes stealing CPU usage.
Csgo is gpu based game so better gpu makes more difference than a better cpu
download process lasso and disable core 0 or something like that made my fps go +50-100
look if cpu or gpu is under locked (maybe because of high temperatures so check them)
disabling uber shaders gave like +100 fps to my friend