What is my problem?

I need somebody to help me to see this game in which I lost so many opportunities... and finally I draw in a very lost position. I dont understand why I play so badly, maybe somebody could direct what should I train to improve.

Your problem is your profile image.

very good match

Probably my problem is the calculating process, isn't it?

Calculation? When did you miscalculate? I'd ask why 23.f5 was an attractive move to you? I really liked it. Both your bishop diagonals and both the f and e files would like to be opened against his king. The exact same sort of move would have been 25.f6 and white should win. This isn't something to calculate, this is just thinking through it logically, which moves make sense.

I still like your position a lot though, that's just sort of a conceptual oddity.

The other conceptual mistake that stands out to me was trading queens. With the queens off, just in general, weak pawns are more prominent in the evaluation (no queen activity to offset the static weakness). After move 35 your pawns are worse and the d pawn is a big target. The only up side is you have the bishop pair. As black I'd already have hopes for playing for a win at this point.

You know what the REAL problem is? The fact you lost. End of discussion, I have spoken. If you won the game, there is no problem at all.

It's too easy, I can't do it

8.Nf6 wins a pawn.
12.Qc8 wins a pawn.

Place a high importance on development. 17.g5 is very bad. Both your a1 rook and c1 bishop want to participate.

When you're attacking the king, instead of checking a lot, try to control the squares around the king (building a mating net).

32.R1d5 threatens mate in 1 (and white will win).

For move 36, any move that protects your g pawn is good (keeping the black king boxed in).