The exchange of Queen for Rook and Bishop was a mistake because you entered the King and Pawn endgame down a pawn. So, the exchange had no real upside potential, mostly downside (forcing you to struggle for a draw with little opportunity to win).
Instead of 50. Kf5, which loses, you might save a draw with 50. g3. For example, 50. g3 Kf8 51. f5 Ke8 52. Kd5 with the idea of Ke4 and Kf4 to force Black to isolate his pawns by an eventual exchange on g6 in order to attempt to make some progress.
I don't see any serious errors in this game on either side, yet I lost in the end. It came down to pawns and kings . Though I thought I could find a draw it escaped me. Advice is welcome.