Games between two 800 rating players are rarely played accurately. You won because your opponent was careless and fell for the knight fork checking the king.
Your rating is probably not in the 800s by the way you played this game.
I wouldn't consider 800 ratings as intermediate chess player, instead somewhere between 1500-1800.
http://www.chess.com/livechess/game.html?id=5421155#
For being an intermediate player who just started playing online chess, I think I handled this player from the beginning. Thoughts?