Plz help me analyze this game: Sit2(White) vs Fide rated (black)- 1.e4 e5 2.Nf3 Nf6 (Going for the Petrov Defence) 3.d3 (Best move is 3.Nxe5 with .....3.d6 4.Nf3 Nxe4 5.d4 (Petrov defence)) .......3.Nc6 (developing) 4.a3? (Useless move -White should develop pieces) .....4.Bc5 (Black gets ahead in development) 5.h3? (Violating all opening principles) ...5.d5! (Extending control in centre-c8 h3 diagonal also opens for the bishop) 6.exd5 Nxd5 7.Be2 (White finally develops) ....7.Be6(The final minor piece is developed) 8.O-O O-O (Bot sides protecting the king) 9.Bg5 (development) ....9.f6 10.Bh4 Qd7 (Connecting rooks) 11.c4 (Better was Nc3) ...11.Nf4! (Outposting the Knight) 12.Nh2!? (Why not Nc3) ...12.Nd4!(Bringing second knight into play) 13.Bf3 (What else)...13.Bxh3!! (A neat tactical sack-14.gxh3 Qxh3 wins for black) 14.Bg3??(14.gxh3 lost but still gave better chances) ...14.Nxf3+ 15.Nxf3 Nxg2!(Bxg2 Bxf4 lost)16.Qd2 Qg4 (Threatening Qxg3-The f2 pawn is pinned) 17.Nh2?? (white failed to interpret the threat)...17.Qxg3!! (White now has a lost position) 18.Kh1(Removing the pin) ...18.Qh4 19.Rg1 Bxf2? (I made a mistake Rxg2 finishes all attacks) 20.Rc1 ?? (My opponent did not notice it !!) ...20.Ne3 (Game finishes in a mate in 1) 21.Nc3 Bg2# (0-1) Plz tell more of my mistakes in this game and help me improve my game !!!