What's the best move by white in this game?

Question

In this game white must win. Please help me.

Answer 1

The key move is the g3 move.

• If the e3 rook is unpinned, black has lot's of troubles
• If the b8 knight is under-protected, Qxb8 wins easily

1.g3 achieves both.

 1.g3 Qc7 2.Rxd7 now wins (Qxb8 or Rxe8 coming)

Black should resign.