10...b5! is a typical way to generate good counterplay for Black.
10...f5? only makes the previous odd white move useful. White should simply touch the f5 pawn by 12.Qc2! when Black must either misplace the d7 knight to protect it, or surrender the e4 square.
12.f4? is a positional lemon- Black is more than OK after 12...e4. White should counter this with an eventual g3-g4, but with a knight on h4 this is far from doable.
13...Ndf6? is tactically wrong, as after 14.Bh3! there is no clean way to protect the f5 pawn.
During the American Civil War, General Grant was trying to get his Army
moving in some very wet and muddy weather. The general came upon a lieutenant,
who seemed to be trying to maneuver his troops and not making progress
going forward. Grant asked him what the problem was, and the lieutenant
told him that he would be in terrible shape if the enemy were to suddenly
attack his flank. Grant replied, 'Don't you know that the enemy is stuck
in the mud also?' In this game, I often dis-parred over the disarray
of my pieces and had to keep reminding myself that the other side was also
stuck in the mud.