lost from a piece up...
Being up on material, you could have considered 16.Rd4, offering to trade a misplaced Rook for a strong Bishop.
And yes, on move 15, there was no hurry to capture.
Your position is a bit better than Black's after 12 Rxb5.
Your first error is 13 Rc4. Your Rook is going to get into trouble there. You should move Rb5 so that you can retreat to b1 if needed.
14 Nd4 is better. The Knight on c6 isn't going anywhere.
16 Qd7! is the move. After Qxd7, 17 cxd7 Rxc4, 18 Bxc4, followed by Bb5 and a4 if needed, you've given up the Exchange, but your pawn on d7 is a thorn that Black can't remove. You can attack d8 with your Knight and Bishop, and Black can't do a whole lot about it. The game might continue 18 ... Bxc3+, 19 Ke2 Ra7, 20 Bb5 Rd8, 21 Rd1 Bb4, 22 Ne5 Bc3, 23 Nc6 Rdxd7, 24 Nxa7 Rxa7, 25 Re8+ Kg7, 26 Be3, and you're up a piece for a pawn with a strong position.
19 Qxe2 gives up a pawn for no reason. 29 Kxe2 is safe in this position.
20 Bd2 of course is a blunder that costs you material. 21 Nd2 avoids the problem, as the Bishop covers c1.
