First of all, nothing you can do will assist you to beat a better player than you.
That said, try moving them side to side, never hit into their strongest hitting zone, slice low and biting, and hit winners when they bounce the ball higher than you like.
Can't do those? Well, then he's a better player. He's seen everyone try to beat him doing those things before.
Drop shot him, use low sharp CC slices.
Or hit harder than he can handle.