4. ..... Nf6 would have been better and then castle for black...
5. ..... Nf6 would have been better aswell if he hadn't done Nf6 on move 4...
10..... Nb8 was a bit passive, i woulda gone for the exchange of knights with 10.... Ne5 11. Nxe5 Dxe5 12. Qxe5 F6.... black is down a pawn, but in the actul game black loses a pawn anyways...
I think not castling is blacks biggest mistake..
Congrats with this major win.... but black made a few errors.
Herman,
8...Bxc3 was wrong. I would have played Nf6 preparing for castling in the next move.