Yes there were quite a few mistakes but some interesting features at the end.
It is quite amazing that even with 2 bishops, white is unable to prevent black from queening after 64... a3. The c3 and c4 pawns really interfere with the diagonals.
You did quite well in constructing a mating net (with your opponent's help) and the final position is indeed pretty.
A queen versus 2 bishops (assuming the pawns get exchanged) is a win for the queen but it takes more than 50 moves. It reminded me of the Stockfish - Houdini game in the TCEC superfinal (season 9 game 17) where it was awarded a win for the queen because it was adjudicated as mate in 72 even though both engines had 0.00 evaluations.
Final position
lichess.org/analysis/standard/K5Q1/8/8/8/5bb1/6k1/8/8_b_-_-_0_72This is the link to the game if anyone is interested
http://tcec.chessdom.com/archive.php?se=9&sf&ga=17