If he plays Nd4 we sure can't take his Knight...
The knight is untouchable,
I don't understand. 19. Bxd4 cxd4 20. Ne2 and we've opened the c-file with slight pressure on Black's d-pawn. Isn't that an improvement on our current position? What am I missing?
If we play Qb3 this will happen:
18. Qb3 Nd4 (attacks the queen).
If we trade:
19. Nd4/Bd4 (takes Knight) d4 (takes Knight or Bishop).
20. Nd4/Bd4 (takes Pawn) Rd4 (takes Knight or Bishop).
We lose Knight and Bishop, while he only lose Pawn and Knight.
If we don't trade:
19. Qa2 ?? (plenty of options, but I doubt he will trade Nf3... he can go later after our queen which is stuck in the corner).