Help me analysing this

Avatar of aldlv
| 2

I had this game recently and i decided to analyse it with chess.com computer analisys... but i am sure that what the analisys mark as a blunder, it's no at all a blunder

so here is the game

 

So my questions are... about
17... f4 (and 18... Rf5, because that's why f4 was for)
and
20... Bb7... because it is was not a blunder.. maybe was not the best, but not a blunder