Looking for someone smart enough to help me

I do know I have a potato PC but what I don't get is why every single game runs at 15fps and it's practically driving me crazy, thought something was wrong so I decided to get just cause 2(an old game)

and it still ran at 15fps check assassin's Creed black flack and it's practically the same thing even for pes17 it all runs at that same 15fps.

 guys is this a setting or what cause it's driving me nuts can someone please tell me how to fix if it is really something a little tweaking can solve😭😭😭😭😭




PLEASE FOLLOW ME GUYS