Where did white go wrong in this endgame

Hello all, what goes wrong in this endgame for white? Can someone explain. I know thats a lucky win :)

white went wrong when he let your king get thru and when he exchanged i dont like Kg2 allowing a c5 played 43.Kg2 better seems to be d4 now if black tries to get thru :

Well he played Kg2.. And why is Kh3?? if he g4 I can take and have enough time run to queenside

look given above is Kh3?? as after Kf3! g4 is guarded so practically the only move is Kh2 or b6(if b6 white plays c4 and its black to move if b5 cxd5 and white will then rush his king to capture it after and exchange on g4, if Kh2 after b6 c4 it's the same continuation as one of the variations given above) if Kh2 i have given the variations above.

51...h4 may have been better

I think white is too eager to trade for a draw, doesn't keep position in mind. I don't see one big blunder, but there are some small positional errors like 36. where kf4 seems more natural 38. where h5+ looks better 41.Ke3 does look like a blunder to me