what you think?

I am black playing the king's indian and the opponent is a friend of mine who clearly did know what to play but ended up winning to a game being won and lost on the black squares!

the grades are english grades if they look suprising to you! 

The exchange sacrifice against the fianchetto king position is a dangerous weapon. 

Was there something wrong with 22. Bxd7. That looks like a hanging piece to me.

22. ...  Ncb6 should save black's piece. (23. Nc3 is met by 23. ... c4) 

10...Bf6 was a mistake. You never want to trade off your fianchetto bishop just for the exchange. That leaves your kingside with huge holes and makes all the tempo gone into making that fianchetto rather wasted. The bishop on the long diagonal is a powerful weapon. Your lucky he didn't trade off, or else you wouldn't have won that rook.

 I also don't understand 19...a6. That leaves your knight weak, opens another hole in your position, and the tempo could have been better spent. His queen wasn't gonna take your knight, and is pretty useless where it was. Notice how it lost you a knight during moves 22-24, and set his queen up for the unstoppable checkmate that you failed to see when you captured the a pawn on move 24. Pushing pawns that aren't center pawns create holes in your position. Don't do it unless it's called for.