(a.) Higher temperatures give a faster rate of reaction. We've seen before that when reactions are carried out at a higher temperature, they have a faster rate of reaction. In the Haber process, a higher temperature would allow the reaction to occur more quickly.
(b) If the pressure is increased, the equilibrium position moves to the right, so the yield of ammonia increases. The rate of reaction also increases because the gas molecules are closer together, so successful collisions are more frequent.