me vs. billaud

2...Nh6 I dont understand this move and I don't understand your comment either

3.g4 your opponent seems to commit to a very strange-looking sacrifice in order to gain time and develop a piece. I believe you played correctly by taking the pawn since Bh3 is probably not the best position anyway for his bishop.

6..Bb4+? does not gain time since you will have to move the bishop once more when he advances his pawn.

7.c3 your OPPONENT gains time. Freeing his bishop while attacking yours

9...Bb6? you should be developing your other pieces instead of moving this bishop for the THIRD time

12.d4 is indeed a relatively good move. it gains central space and blocks your only "active" piece, the dark squared bishop. white has a clear advantage in development and space

12..g6? another poor move that weakens your king. At the moment it seems like white is unable to apply any more pressure and you should definately have played d6 for that reason, freeing your pieces while threatening his knight.

15. ...Bh3+ a good move, developing a piece with tempo. THe opponent's king is stuck in the center and his lead in development is diminishing 

16.Kg1 and so your opponent falls falls for a tactic, hanging a piece.

I think you need to follow some principles. 1. Develop all your pieces. 2. Dont move a piece twice in the opening 3. Try to control the center. If you follow these principles I believe you will improve your game quite a bit. Your opponent seemed to be aware of this and quickly gained an advantage. Lucky for you he wasn't so good at tactics as you were it seems