If the game is a steam games, then yes. What you buy from Gamestop is a code that you input into your steam client that activates the game, and allows you to download and play it. Gamestop also sells Steam cards.
can i download i game from gamestop and play it with steam and steam freinds. and how
Gamestop will give you a CD-key. You can simply go to steam and redeem the game there using that Cd-key. Some keys or games are not compatible with steam and won't register. If that's the case you can simply choose to add a nonsteam game to the library. That way the game will show up on steam and you should be able to play it with your steam friends from there.