Could someone look at this game?
34...Rxf3+ 35.Rf2 Bh3+ 36.Ke1 Qg1+ wins for black.
After you won the pawn on a7 you must be better. Perhaps Nd5 was a good move for you as you mentioned. After that is difficult to pinpoint exactly where you went wrong, I think black conducted the kingside attack well skillfully exploiting your weakened dark squares.
what's wrong with 35 Kg1! ?
23 Qd6! trading Qs looks good.
Nd5 , when?
I'd really like it if you provided more commentary on your moves before you posted, but here are my thoughts:
Instead of 9 Bf4, I prefere h3. Your bishop belongs on e3, and h3 prevents both Bg4 and Ng4, and it's a fairly well tested move in double fianchetto of the KI.
Missing 16 Nd5 is very, very easy to do. I would never feel bad about that. Anyway, 16 Rd1 is a great move, and might even be better. Where you really missed Nd5 was move 20.
What you want to know is when you gave up on your own plans and instead starting reacting to Black. There's a good argument to say this happened on move 17. Because of your queenside majority, you need to focus on your advantage there, Black's plan be damned (for as long as possible). You could have kept the initiative with 17 b4! or even Bg5. After 17 b4! Nd7 18 exf5 gxf5 19 b5 you are following your own ideas, not Black's. In my experience, it is almost always bad when Black gets his pawn to f4 in the KI.
I think black conducted the kingside attack well skillfully exploiting your weakened dark squares.
I think the attack was only successful because of the time pressure. There was too much play in the center for to focus only on the kingside, and until White blundered on move 30, there was no real mating threat.
it all seemed losing so that's why I tried passive defense.
Erad, with all due respect, I think you need an attitude adjustment. You own a good rating, but it would no doubt be 100 points higher (at least) if you adopted a positive, fighting attitude toward all chess positions. You were winning all the way through the first half of this game, but thought you were losing. Even after you were a clear pawn ahead, you gave yourself 'equality.' 
Even when you are losing, a passive defense will never change things. It's better to go down swinging, and quite often your opponent will be intimidated and commit an inaccuracy.
Good luck!
When black played f5, I would have exchanged pawns without hesitation rather than expose the king with f3. The exchange strengthens white's KB, leaves black with an isolated pawn in the center and gives white a tempo to shore up the kingside defense.
Black can bring his rook to the f-file with Rxf5, but as we saw in the game, it's hard for white to prevent this. As long as the bishop is on e3, the threat is contained. While black is scheming to trade off the e3 bishop, white can consolidate his position.
A grandmaster . . . Nunn, I think -- said that after you win material, your pieces are scattered and your next task is to gather them and restructure your position for your next goal. The other side usually gains some time by this, even in accidental and one-side losses of material like the one in the game. All you needed to do was to defend carefully, but you seem to have overreacted to black's pressure. So I would suggest you keep your cool and remember, as Nunn implies, that you can expect your opponent to gain a little time when you capture material. Just defend well, and his or her initative will subside and you will still be up a pawn.