Giuoco piano, dangerous bishop sacrifice by opposition player, how to deal with it ?

Hello eveyrone,

EDIT: Sorry it was a knight sacrifice. 

In the game I'm going to post, I had a knight sacrifice, that was difficult for me to deal with. However opposition player abandoned the game for no reason so no result. What surprised me in post match analysis is that engines show that it was completely justified and with perfect play it would be a draw. Questions I have

1. Why is it justified, makes no sense to me? Hasn't the player lost a knight

2. After this sacrifice can anyone show me a way yo unpin my knight

3. Forget about the sacrifice I want to know about this bishop pin from queen side, opposition player move bishop to g5. Since my bishop and knight can not defend the knight, can I ever unpin this knight. Tell me the way to unpin this knight without having to extend pawns in my king side castle side. If not possible how do I avoid this notorious bishop pin. 

Thanks a lot

1. Because you overextended you kingside pawns. I would totally go for the sac there too. White loses a knight, but black gets attacked. "World champion Magnus Carlsen knows something you don't. When you checkmate someone, you win the game" - GM Ben Finegold

2. Qe7-Qd6

3.

The simplest way to avoid this Bg5 stuff is to play h6 before d6.

If Bg5 comes before you played h6, you have the option to unpin with Be7.

Another way to avoid the sac is to not castle so quickly as Black.  I always play ...d6 and sometimes even ...h6 before I make a decision on castling. 

Just don't play g5/g4 unless it sounds reasonable. If your opponent does Bg5/Bg4 just do a simple h6/h3, but don't continue with your other pawn, because then your king safety is really destroyed

Correct, those pawn moves creates major weaknesses and opponent can exploit using a rook pawn to break that structure. In most of the cases it is a weakening move, sometimes it works out well.

Don't play g5 or g4 if you're gonna castle there period

Is that sacrifice really justified? I'm not so sure. White hasn't finished his development and can't rapidly bring up more pieces to reinforce the pin. 

F4 rook lift. Neither can black go defend easily

I see all that, but it looks pretty slow to me. I know that defending in easier for engines than humans, but the fact that Stockfish 11 at 35 ply assesses the position after 10.Bg5 as -2.52 is significant.  But I could easily be convinced by any concrete lines

it's probably not sound, but the psychological/surprise effect has to be considered. Probably was something I'd play when I was rated <1500

Me too! In fact, I could easily play it in a fast time limit game

Glad to know we both like unsound sacs to some extent

Hey thanks for all the replies. Lasker you are right i saw the engine line and if black holds his ground firmly for about 6 more moves,  he can unpin the knight and human white player will more likely to lose. However next 6 moves are crucial for white where he has the best chance of winning.

Thanks for snudo and others for their help as well. I read all that and i still have a question. Previously when i have posted my lost games here many commented i have a bad habit of playing a3, h6 early and losing time for development. Then i decided i would plau a3 and h6 only after my development and castling complete. Now you guys are telling me to play a3 early, also with a3 early i have fallen to a notorious bishop sacrifice on castled king as well. So what should i do i'm confused. Thanks

If you’re going to play those moves, it weakens the kingside making it suspectable to bishop sacs. It doesn’t REALLY protect the square you intend it to.

So sometimes delaying castling is a good idea, so when you weaken the kingside you don’t castle there. Now, it’s an aggressive weapon and not a weakness.

Ok snudoo, thanks for the tip. I will try this for the next few games. 

you can play h6 on move 4 if you want to get rid of this stuff altogether. normally such a slow move should be punished by a central pawn breakthrough or sacrifice but here white doesn't seem to have that. black intends d6 next and only then nf6. you would prefer to be able to capture on e5 with a pawn in case of d4-xe5. some crazy stuff like 4..h6 5 bxf7+ kxf7 6 nxe5 nxe5 7 qh5+ looks scary but shouldn't work for white. you have to study this as this is probably the trickiest line and it is forced for black but also it is probably winning for black as well so you shouldn't mind some memorization. and it is fun too.

@ Snudoo: I just followed your advice and won a game with a high rated opponent. I dedicate this win to you. The annoying bishop pin came and I delayed castling like you said and led an attack. Could you please look at the game and tell if I did ok, because I feel like playing like this always if that annoying bishop pin comes again. I exchanged queens without thinking, would it have been easier for me if I kept the queens. Also should I continue this or, did I just get lucky in this game. Thanks a lot

Ok, first of all, white was perfectly fine out of the opening, but you did miss a win of a piece. I'll show you what I meant when I said to play g5: