Chess Game: 1 b4 e5 2 Bb2 Bxb4 3 f4 exf

Please, I need your advise, where did it go wrong?

Difficult to say where you went wrong but nonetheless an interesting game. I believe this variation with 3.f4!? is called the Kucharkowski-Meybohm Gambit and it takes some courage to play this one... I think after 24.Kh1 Black stands better. Doubling on the f-file with 24.Qf3 looks good also to prevent the strong Nf5.

Yes, it is the K-M Gambit. I have played it once on the real board, but lost and made a huge mistake in the end game. I always play this one on the internet, to feel confident when somebody accepts this line on the real board.

I agree that move 24. Kh1 is the suicide move. But what to play instead? This game wasn't easy, was no fun, because had to play precisely. I often have such games as black on the Caro-Kann, but at the Sokolsky opening, I seldom have to play precisely.