Wow. Keep going, try to think in the value of the pieces, giving away your pawns for nothing, and a knight for a pawn are not good moves. That goes to both of you. Other than that, learn one or two openings and all the variations.
Caissa be with you! ;)
Very nice to find the checkmate.
E4-D5 is the center counter or scandanavian opening. F3 is a response that recovers the center if he takes your pawn. A simple d3 and his queen is a centralized target with little to do out there if you do not make any mistakes. If you goof up, he can take half your stuff. C3 is bad, you give up a pawn and check for nothing. It is good that you looked at an alternative line, and yes, the alternative line where QxQ KxQ is bad for white. exd is the most played line for white; queen takes pawn and its game-on for central queen (both an asset and a target) vs white's game.
7) Bf4 is "ok" but you end up losing the bishop for nothing. You need a plan, to either defend it or move it to a better place or something next move. H3 is like c3, its a pointless pawn attack and it cost you a piece. Bxc7 is much better.
14) he gives the piece back, your lucky day. Doubly so since all his other stuff is stuck in starting positions.
17) a4 is ok but Bc4 lets you trade a pawn for a pawn or if he defends, you can also defend your pawn.
And for your friend....
10) ok, great so far, you won a piece. Your queen is played, though, she can't do anything productive up there. Trade it -- as you did --- perfect.
14) Nxd4 gives up a piece for a pawn. While nice to release your rook, the rook cannot do enough (ignoring mistakes) to justify it right now.
19) rooks are worth more than knights or bishops (mostly, because you can checkmate with a rook and a king, but not a knight or bishop and a king). Bad trade.
20) hindsight and all that --- the mating attack is not obvious at all to novice players (again, your friend did well to find it!).
In general, you needed to move out your other knight and bishop. Not doing so means that even if he had not had that forced checkmate attack, you were still in a bind at this point.
We are beginners, but we are crazy about chess.
And want to improve our chess skills.
Please advise us about this game!
(Sorry for my poor English.)