Stalemate with a higher rated opponent

The game ended in a stalemate with a higher rated opponent. Surely both of us made many mistakes, but its worth your comments / suggestions on what to do or how to play against an experienced opponent.

Black made only a single fatal mistake in terms of a mistake's significance. Your opponent's last move should have been queen on b6: checkmate. The bishop on c7 led up to the stalemate.

I'd say White pushed too many pawns. Try developing pieces instead.

how black could prevent a stalemate,with advantage.