Where did I go wrong here

Pretty sure on move 26, you could take black's light squared bishop, cause if he moves his dark squared bishop out of danger, then you take f7, forking the king and rook.

Qb6 decided your fate, I would have went Qd3 and start pushing pawns maybe? cuz like that, the queen can always retrear to Qf1 and guard the king. Try to trade queen and steadily puch your a,b,c pawns. That's all, correct me if i'm wrong.

after Qg5 you should have played Qf1 to avoid the mate

Qd6 would have also worked yes

You got into trouble because it was an odd situation with bishops of opposites (and incidentally 36... Bf3 looked pretty strong). A bit later on you had say 39 Qd3+ and you're safe (and can start to push those passers).

But be very careful going up against opposite-colored Bs in an attack because mating nets can suddenly spring up (and your bishop just ends up looking like a phantom).

yeah qd6 would have worked

As Jerry said, with 8:45 remaining on your clock you used zero seconds on a game-changing blunder. Using time effectively is something that most people struggle to do well. Me included.