It is mad to go into endgame against a GM where he shines as bright as the sun.

This was a strong opponent.   He played good provoking moves to undermine your position.

I recomend not reavling the winner in the title, because then the suspense is gone.

Why is it impossible to beat gm players

You didn't play correctly the position very similar to the king-indian; you gave black easy, comfortable game after....f5.  The great Efim Geller, Fisher, Kasparov, and many more loved black in that setup...You need to study how Vladimir Kramnik played as white against Kasparov and others and had many wins....It's classic now and the recommended way for white....At the end, I thought you must play Nd1 and Ne3, to prevent his e3 and control g4.  This was the right plan for you to hold the position.  Black was still slightly better, but f4? ain't move a player like me (former 2500+) would ever consider even in blitz...

Was queen A4 before he castled to win the pawn a mistake (you did not play that I'm just asking, because looks like you are winning a pawn and pinning the knight)?

i dont see why you played c4 so soon. white looks rigid already

Something seems not right with White's opening play and setup, but I'm not certain what it is. The position resembles an Old Indian or King's Indian, and a white bishop on d3 is rare in those variations, maybe it's that. The GM plan of Ne8, g6, Ng7 intending f5 is very interesting, and often seen in the Czech Benoni: 1.d4 Nf6 2.c4 c5 3.d5 e5 4.Nc3 d6 5.e4 Be7 6.Nf3 O-O 7.Bd3 Ne8 8.h3 g6 etc. I'm not certain it's very good in that line but works well in this game in the video

your camera focus is often not on point.