Every curved arrow tracks electrons. Never atoms. Two electrons, one arrow.
The tail sits on a lone pair or a bond. That's the nucleophile, rich in electrons.
The head lands on the electrophile. Here, carbon, pulled thin by bromine.
Carbon can't hold five bonds, so the C–Br pair leaves with bromine.
Answer: draw arrows from electron pairs toward electron-poor atoms, giving CH3OH plus bromide.