Not exactly, as although the king is exposed, there is no good way for White to forcefully attack it. So Black's king is reasonably safe.

White's very first threat!

This doesn't win any material for black - and it leads to another key point when thinking about your move. You want to move your pawn - but is that pawn protecting anything? If so, that piece could be unprotected after moving the pawn. As it turns out, the pawn on c7 was protecting the bishop, and white can escape with 13. QxB PxN 14. QxP and it's now black who is up material

My preference here would have been R or Q to f6, keeping the pawn (12...Qf6 13.Nxd6 cxd6 with an OK game for Black.

Oh dear...

Too trusting of one's opponent, and not trusting enough of oneself. 13.Qxd6 won a pawn, possibly two ( 13...cxb5 14.Qxe5 attacking b- and f-pawns).

...

We know this is a pawn. In annotating the game, you should tell us what you were trying to achieve here - why did you make this move? Then you'll learn from the comments posted. As jkarp says, 15. ... Nc6 was really worth considering as it brings another piece into the game - and pieces are worth more than pawns, so it makes sense we should try to play with them where possible.

The bishops on c1 and c8 are staring dolefully across the board at each other, completely unable to move even 18 moves into the game. A sad state of affairs!

20. g3 wins material for white because the bishop is pinned.

Black has a strong threat here, but it is true that 20.g3 would win back a piece for White. Not that it would help much after 20...Nd4, say.

Instead 20...Bxh2ch 21.Kxh2 Rxf1, and, on account of the mate threat (22...Qh4#), White loses the B on c1 as well. White was never really in this game...