wwall: So what is the losing move? Perhaps 32...fxe5, later allowing Qxe5 and control of the center. Black could hold better with 32...Kf7 or 32...Kg7.34...Rd6 looks weak and loses a pawn. Maybe Black should try to exchange queens with ...Qc7 or ...Qg7.
36.cxb6! was good. Black cannot play 36...Rxe5? 37.Rxc8+ Kg7 38.R1c7! and wins for White.
37. b7!, threatening to queen and win despite queen and rook hanging. If 37...Rxe5, then 38.b8=Q+ Qf8 39.Qxf8+ Kxf8 40.Rxc4 should be a won endgame. Same with 37...Qxb7 38.Qxe6+ Qf7 39.Qxf7+ Kxf7 40.Rxc4.
Instead of 40.a5 (threatening a6), perhaps 40.Qg5 is stronger, trying to exchange queens and remain a pawn up.
Same for 41.f5. Better may be 41.Qg5.
42...Rd5?! and 43...Rd7 seems a waste of tempo. Perhaps just 42...Rd7 or 42...Rc2 and 43...Rg8.
Instead of 43...Rd7, maybe just 43...Ra8.
Instead of 44.Qb3 (White threatens 45.Qxf5+), why not 44.Qh6 and Qxh7, winning another pawn.
44...Ke8? allows 45.Qe5 (threatening Qh8+) and a strong center that wins. Perhaps 44...Qf6 instead.
45...Rd5 looks bad. Slightly better but still losing may be 45...Kf7, but then 46.Qxf5+ Kg7 47.Qbxe6.
Instead of 46...Kd7, if 46...Qf8, White wins after 47.Qxf8+ Kxf8 48.a7 Ra8 49.Qb7.
After 49.Qb6+, White mates in a few moves. If 49...Rc6, then 50.Qcb8+ Kd7 51.Q6b7+ Rc7 52.Q7xc7 mate.