Moving the white square bishop up and to the left one to threaten white's rook seems pretty good to me. The computer won't be able to prevent the loss of material I believe.
What is the best move for Black now?

In other words, 1...Bh3.
But the computer will be able to prevent loss of material with 2.Ne6 or 2.Be6.
Your best move isn't Bh3.

It can prevent the loss of material, but you're giving away your bad bishop for either their good bishop or a knight.

What everyone is trying to say is 1...Ba6.
This is probably the best move for black. After 2.Bd3 Bxd3 3.Nxd3, white has lost the bishop pair and the strongly placed knight is now on a worse square. This plan for white seems a little better to me than 2.Nd3, leaving the knight on d3, pinned to the still immobile rook. This is the best thing I can come up with for black in this position.
Hi Toufiq,
What is White threatening? There is a possible fork by the N on e5 but that is defended by the Q at c7. Unsound sacs against the Black pawn on g6 by the Bc2 or the Ne5 just open the g-file again. Most of White's pieces are on the Kingside and access to g6 through center is blocked.
Strategic Analysis: The center is closed and White cannot open it without
considerable loss in material. A queen side attack by Black
against White's castled position is indicated because the
center is closed and White will not be able to counter there
against Black's attack on the queenside wing. Also Black has
3 minor pieces(B+2N) on that side of the board vs. 1 White
N(Knight) and the R on f2.
It would be very good for Black if he could pin down White's
pawn at g2 because it will make it very difficult for White
to defend his castled position along the rank a2-h2.
Advancing the pawn will permit the opening of the
g-file which would not be good because of Black's
Rook on g8 and White's King on g1. Sacrificing the Knight
with 1...Ng3 is unsound. However, 1...Nf5 is excellent. It
locks down the center, brings the one knight on the rim to
the attack and begins to make the sac on g3 sound. Note
that not even the pawns at g2 or e3 can drive the Black Nf5
off his outpost as that would open the g-file. Next
will come the Black Queen over to ...Qe7
I think you can take it from there.

transpositions wrote:
Hi Toufiq, What is White threatening? There is a possible fork by the N on e5 but that is defended by the Q at c7. Unsound sacs against the Black pawn on g6 by the Bc2 or the Ne5 just open the g-file again. Most of White's pieces are on the Kingside and access to g6 through center is blocked. Strategic Analysis: The center is closed and White cannot open it without considerable loss in material. A queen side attack by Black against White's castled position is indicated because the center is closed and White will not be able to counter there against Black's attack on the queenside wing. Also Black has 3 minor pieces(B+2N) on that side of the board vs. 1 White N(Knight) and the R on f2. It would be very good for Black if he could pin down White's pawn at g2 because it will make it very difficult for White to defend his castled position along the rank a2-h2. Advancing the pawn will permit the opening of the g-file which would not be good because of Black's Rook on g8 and White's King on g1. Sacrificing the Knight with 1...Ng3 is unsound. However, 1...Nf5 is excellent. It locks down the center, brings the one knight on the rim to the attack and begins to make the sac on g3 sound. Note that not even the pawns at g2 or e3 can drive the Black Nf5 off his outpost as that would open the g-file. Next will come the Black Queen over to ...Qe7 I think you can take it from there.
Thanks you guys a lot. You know I really a rookie in Chess. And the analysis are helping me a lot.

transpositions wrote:
Most of White's pieces are on the Kingside and access to g6 through center is blocked.
What I think you meant to type was White's pieces are all on the Queenside and his King poition is in potential danger due to Black's pieces already there and better mobility by his remaining to get there.
I'm looking at 1..f6 2. Nd3 (Nf3, Ba6! winning material), Ba6 followed by g5 prying open lines and diagonals to the King.

I would play Ba6 followed by Nf5 eventually (but if you do this move, watch out for the g4 pawn push by white, forking both your knights!). The theme here is you need to focus on reactivating your minor pieces.
You might also consider a bishop for knight trade since you've got a pretty closed match and his knights currently outweigh your bishops. This scenario could be reached via Bf6 followed by Bxe5.
Thanks