13.Bxf6?! Nxf6
A little dubious for him to give up the two bishops voluntarily.
14.a4 Qb6 15.Nd2
It's usually a good idea for white to trade light-squared bishops here.
15...Bxg2 16.Kxg2 Rfc8
Playing to open the queenside.
17.Qb3 Rab8 18.Qc2 Nd5 19.Rdb1 Nb4 20.Qd1 Rd8 21.b3?

Although white was trying to stop c4, he now weakens the a1-h8 diagonal. Here I realized that I had the advantage because of his dark square issues. [21.Nf3 was much better, with the idea of meeting 21...c4 with 22.d4 . Although white is still worse here, he can still play a reasonable game.]
21...Bf6
Now my dark-squared bishop becomes very powerful.
22.Rc1 Nd5?!
Instead of this I had a way to win very quickly. [22...Nxd3! 23.exd3 Rxd3 And white finds both his knights caught in pins that are impossible to escape. For example 24.Ne2 (If 24.Nce4 Bxa1 25.Rxa1 f5 traps white's knight.) 24...Bxa1 25.Rxa1 Rbd8 26.Ra2 Qc6+ followed by Qd7 wins back the knight on d2, leaving black up an exchange and two pawns.]
23.Nde4?
After this move I was pretty confident that I was going to win. [23.Nxd5 was the only way to stay in the game. 23...exd5 24.Rab1 b4 is still much better for black because of his queenside majority.] 23...Bd4
Keeping the pin and building up pressure on white's queenside.
24.Rab1?
This move just blunders a pawn and causes the complete collapse of his queenside. 24.axb5 axb5 25.Rab1 This is still significantly worse for white, but at least it doesn't lose material. 25...Nb4 26.Nd2 e5 and white is basically paralyzed.
24...Nxc3 25.Nxc3 Bxc3 26.Rxc3 bxa4 

Now the pin on the b-file is very hard to break.
27.b4
During the game I saw the line 27.Ra1 axb3 28.Rb1 c4 , which keeps the b-pawn alive, and after 29. Rxc4 Rd5 30.Rc3 Rb5 black will simply push the a-pawn and promote.
27...cxb4 28.Qxa4 Qb5 29.Qxb5 Rxb5 

This double rook endgame is easily won for black.
30.Rcb3 a5 31.Kf3 Rc8 32.Ke3 Rc2 33.d4 Ra2 34.Kd3 Rb8 35.R3b2 Rxb2 36.Rxb2 a4 37.Kc2 Rc8+ 38.Kb1 b3 39.e4 Rc3 40. Rd2 a3 41.Rd1 Kf8 42.d5 exd5 43.exd5 Ke7 44.d6+ Kd7 45.h4 Rc6 46.Rd3 a2+ And the threat of queening after 47. Kb2 Rc1 caused him to resign.