Complex sentence: He tells them that outsiders, both living and dead, will try to gain entry and reiterates his earlier point that the people of Alexandria must be ready to make tough choices, and that he will teach them to survive.
Split into simpler sentences: He tells them that outsiders, both living and dead, will try to gain entry. He again tells the people of Alexandria that they must be ready to make tough choices, and that he will teach them to survive.