You had a large advantage in the opening, which gradually got smaller. But you were still fine, and you had a chance to get a winning advantage with 28.gxf4. What did you think you saw that kept you from grabbing the piece?
Black returned the favor by not playing 31...Qxf3 which looks like a clear winner for Black. 33.Qxc5? should have been followed by 33...Re2+ with a crushing attack for Black
on 28.gxNf4, I didn't want to open up the g file giving white's queen access.