I solved as mate in 5 which coincides with your moves shown. Nice.
Edited to add, - You missed a sequence, where white could screw up by capturing the queen, instead of mating in 4.
Edited again - looking closer after noticing something, I now see that black can stop the mate if white tries to follow through. Proper for white is to capture the queen as i see it. Figure it out on your own, or message me for the moves which I am seeing.
Apologies - The different sequence I saw after playing out on the board is still Mate in 5.
During this bullet game, my opponent found a brilliant M6 but failed to follow up with the checkmate, allowing me to win on time. Can you find the solution?