What's wrong with the way white is playing?

Question

I have played an opening I can't find anywhere online. So I'm guessing it's wrong. Can someone tell me what are the weaknesses in white's strategy? Or is it simply a matter of black not being able to penalize him?

From which move does white and black start to misplay?

[FEN ""]
[Event "Rated Classical game"]
[Site "https://lichess.org/ETe2HGt5"]
[Date "2023.09.26"]
[White "a_saint"]
[Black "hamstra"]
[Result "1-0"]
[UTCDate "2023.09.26"]
[UTCTime "10:54:15"]
[WhiteElo "1747"]
[BlackElo "1810"]
[WhiteRatingDiff "+20"]
[BlackRatingDiff "-110"]
[Variant "Standard"]
[TimeControl "1800+0"]
[ECO "C40"]
[Opening "Latvian Gambit: Mason Countergambit"]
[Termination "Normal"]
[Annotator "lichess.org"]

1. e4 e5 2. Nf3 f5? { (0.29 → 1.65) Mistake. Nc6 was best. } (2... Nc6 3. Bb5 Nf6 4. O-O Nxe4 5. Re1 Nd6 6. Nxe5 Nxe5 7. Rxe5+) 3. d4? { (1.65 → 0.49) Mistake. Nxe5 was best. } { C40 Latvian Gambit: Mason Countergambit } (3. Nxe5 Qf6 4. d4 d6 5. Nc4 fxe4 6. Nc3 Qf7 7. Be2 Nf6) 3... fxe4 4. Ng5? { (0.48 → -0.66) Mistake. Nfd2 was best. } (4. Nfd2 d6 5. Nxe4 exd4 6. Bc4 d5 7. Qh5+ g6 8. Qxd5 Qxd5) 4... d5?! { (-0.66 → -0.05) Inaccuracy. exd4 was best. } (4... exd4 5. Nxe4 Nc6 6. Bc4 d5 7. Qh5+ g6 8. Qxd5 Qxd5 9. Bxd5) 5. c4?? { (-0.05 → -2.55) Blunder. dxe5 was best. } (5. dxe5 Bb4+ 6. c3 Bc5 7. Be2 Ne7 8. c4 h6 9. cxd5 hxg5) 5... Be7?? { (-2.55 → 0.45) Blunder. exd4 was best. } (5... exd4 6. Qxd4 h6 7. cxd5 hxg5 8. Nc3 Nd7 9. Bb5 Qf6 10. Qxe4+ Kd8 11. Bd2 Bd6 12. Qe2) 6. h4? { (0.45 → -0.98) Mistake. dxe5 was best. } (6. dxe5 Bxg5) 6... Bf5? { (-0.98 → 0.36) Mistake. exd4 was best. } (6... exd4) 7. g4 Bg6?? { (0.30 → 2.29) Blunder. h6 was best. } (7... h6 8. gxf5) 8. h5?? { (2.29 → 0.22) Blunder. Ne6 was best. } (8. Ne6 Qd7 9. cxd5 c6 10. h5 Bf7 11. Nxg7+ Kf8 12. d6 Kxg7 13. dxe7 Nxe7 14. Nc3 Rd8) 8... Bxg5 9. hxg6 h6 10. dxe5 Bxc1 11. Qxc1 d4?! { (-0.04 → 0.92) Inaccuracy. Ne7 was best. } (11... Ne7) 12. Qf4 Nc6?? { (1.05 → Mate in 1) Checkmate is now unavoidable. Qe7 was best. } (12... Qe7 13. Nd2) 13. Qf7# { White wins by checkmate. } 1-0

Answer 1

First of all, the strongest move after black's f5 is Ne5, threatening Qh5. If the black attacks the knight with the Queen/Knigth then it can be guarded by playing d4.

Moving on, white should've captured on e5 instead of Ng5 anyway but we'll leave it be. The worst blunder in the opening is playing 5.c4 after which black can take on d4 and later play h6 which seems simply lost for white given the eval is -3 at this point. 5. ... - Be7? again gives the opportunity to re-caprute on e5. This seems to be the crucial pawn and also the square for white's pawn.

So yeah, white should've got punished for giving away pawns and the center so easily. Basically as white you should aim to punish bad opening such as this right away. If you play well, black shouldn't be able to get away with something like this in a Classical game