Complex sentence: Hai is aware that his servant is an impostor, but acts as being unaware, as he didn't have time to train another eunuch for his cause and he has a plot to force Wei to work for him.
Split into simpler sentences: Hai is aware that his servant is an impostor, but pretends that he does not know. Hai does not have time to train another eunuch for his cause, and besides, he has a plot to force Wei to work for him.