Он спросил меня, что я буду делать вечером. Я ответил, что не знаю, буду ли я свободен вечером, но сказал, что если буду свободен, то позвоню ему часов в восемь.
He asked me what I will be doing tonight. I answered that I do not know whether I will be free in the evening, but said that if the will is free, you'll call him hours to eight.
He asked me what I would do in the evening. I replied that I do not know if I'll be free in the evening, but said that if I'm free, then call him at eight o'clock.