Help me understand

This is my first time to post here ... so please execuse my mistakes ... and thanks in advance .

c3 allows the knight b3, so I do not think it is an optimal line. 

18 Nf3 is a little better simply because you rooted a knight deep in his territory.  Deep knights reduce your opponent's mobility from fear of forks, captures, or having to guard pawns, etc.   Here, for example, his rook is bothered to guard a pawn now and his bishop is under attack.   These are future possible moves that may soon help you a lot, so your overall positional score is a little better. 

What you did was fine however.  The difference is tiny, and the trades improved your situation somewhat, giving an open file for the queen, taking away his strong bishop. 

19 b3 seems right, followed by Rc1 or c4 (depends on what he does, if he attacks rook with knight, Rc1 seems useful and later I think you may even find a way to trap the knight).   If he retreats c4 seems good.  Re1 later seems to be a future idea.

There was no reason to resign; in fact I think you can win his knight with some creativity.  Rc1, Qb2, Nc4, and the knight will be yours if I am not mistaken??

Nevermind, Rc1 leads to a family fork, duh.

With that issue, you had no outstanding moves that I could find, and face an uphill struggle for sure.  Maybe not quite resign material but best I have after that is Re1, and really you need black to make a mistake soon.

A... a family fork?

Re1 looks better

I wouldn't resign here. I'd play Rde1. the e7 square is weak. Black has weak dark squares around his king. I'd try to play moves like Re3, push my h pawn move the rook to the h-file and checkmate his ass.

yea it gets the king & queen and rook.  Forking 3+ pieces is a family fork, I think, its been a while on the exact term.

Here is the wikipedia comment on the names for exotic forks:

A fork of the king and queen, the highest material-gaining fork possible, is sometimes called a royal fork. A fork of the opponent's king, queen, and one (or both) rooks is sometimes called a grand fork. A knight fork of the opponent's king, queen, and possibly other pieces is sometimes called a family fork or family check.

so apparently my idiotic suggestion was best described as grand fork, though family fits as well.

I acturally think that white has a BETTER position here. Black has weaknesses. (backward e pawn, weak dark squares around his king) White has all the attacking chances. Do you see how black's king side is weak?

Yes, its weak, but you can't get at it!  White's rooks are bottled up badly for a few moves, there is not an easy way to strike the weakness beyond maybe getting the pawn on e, however after Re1 black plays Re8 probably so that is not an immediate gain either.   White can take 2 moves to drag his knight over to try to hit at the black king, losing pawns in the process, maybe, but is there a winner in that?  I don't see it.  A crazed f pawn push maybe?   Im looking at it, but I see strong counters to all I find.

What about 22 Qb6, Ne2+ is met with Kh1, the b3 pawn is defended, and black threatens the capture on b7. The position is still better for black, but Qb6 gives white chances.

Qb6 is met with NxR not Ne2

making Re1 the only real choice unfortunately.

Qb6 is still better than my first idea though :)

Fair enough

Thanks all for the feedback ... It helped a lot to see how other evaluate the position.

@Jonnin: Agree Nf3 is better. but on 19.b3 allow the knight the c3 square and even with the fork on queen and rook. beside of the very weak pawn on c2 and black has total control of the f file. Can you tell me your thought of why 16.Bxf6 is better than what I did? thanks for your comment.

@Chesswasteland : True black have some weakness .. but do you think white has anytime to exploite them. I mean look how his knight is deep and the c file control and soon the rook and queen will invade to my second rank and I'm all crowded defending. Thanks for your comment.

@eightdogs: yes .. as jonnin said NxR .. the only move here is the sad Re1 and I may be in zugzwang. Thanks for your comment. 

b3 vs c3 was in reference to the alternate line.  He can't fork there, and b3 prevents his knight from getting to the square to threaten the fork.

so, working the alternative computer line.. my 10 cents on it.  However, I think your line was FINE and the alternative is, if better, only very slightly better.

or, wisely instead of Ne6 black saves his bishop from the knigth attack?  I meant to insert that line and did not.  /shrug anyway a good rule of thumb is to ignore less than 1.0 changes in score during computer evaluations.  When it starts saying 0.5 becomes 2.25 or something, that is the time to listen to it.  Things like 0.1 changes to 0.25 on a depth of 20.... its no longer you playing, its the computer playing with a 20+ move look ahead to gain a tiny bonus.   And, I swear it, I think the computer algorithms are rigged to favor position where IF the opponent plays anything except the best lines, the gains are bigger (basically, favoring traps).

Last thoughts...

PC says that Nd5 leads to NxN.  If your pawn takes, he gets your bishop for free.  So you must play BxB.  After all that he still plays Na4 and it claims that NOW after the trading, black has the initiative and attack --- his knight has the fork, his battery has the pawn, and you will lose at least a pawn?

why not 16 Bxf6 Bxf6 17. Nd5 Qc6 18. Nxf6 exf6 (the point of capturing with the bishop in the first place, you were able to fork the queen and bishop.) 

Now, Black has no bishop, weak king, and weak pawn on e6.

seems solid to me

Although, the computer's line, (I'm assuming it's a computer, you didn't say where you got the line from) looks nice visually. blacks queen could potentially get attacked on c6 by the knights, c3 pawn closes down counter play from the bishop on the long diagonal and on the c file, and there's no quick way to bump the knight off of d5, because of forks on f6 and e7.

@jonnin: Oh my bad .. true b3 looks fine and it really reducing the knight effect... thanks for the tips ... 

@paulgottlieb: haha yeah about the Bb5+ doesn't look good but I was saying to myself that the white bishop in the sicilian( It transpose) is bad anyway.. but now I would think twice before giving up my bishop.

so the reason to take the knight on f6 for the bishop is only to play Nd5 but wouldn't he later play e6  kicking the knight and play Be7 to protect d6 and they say d6 is not that weak in the sicilian .

on 17...Nf4! ... you got that right ... I didn't figure what the idea was .. thanks 

Thanks a lot for the feedback and the tips ... By the way I resigned this game but in the second one I won .. though I had some difficulties and felt bad cuz he's a little lower rated than me .. but I won ;)

@KiwiJuise: I know .. I thought the same at first but the "computer" line doesn't take the bishop ... so I figured the Bxf6 is only to clear d5 for the knight .. but again if NxB black king looks solid beside the d6 weakness ..

thanks for your feedback :)