Question, on Steam then you will add the achievements ?
Viewing post in Frankie's FunClub! (COMPLETE) comments
If you buy the game privately it should not show anything. To do this when you proceed with the payment you get a window that says something like “for my account”, click on it and you get an option that says “for my account (private)”.
As far as I understand when you buy a game in private it doesn't appear public in your Steam list, it doesn't send the message to your friends that you are playing that game and it seems to me that it also hides the achievements in your profile.