Complex sentence: Donatello, who has developed a crush on April, is able to rescue her and while Kirby remains a prisoner of the Kraang, she becomes an ally of the turtles, who try to help her locate her father.
Split into simpler sentences: Donatello, who has developed a crush on April, is able to rescue her. While Kirby remains a prisoner of the Kraang, April becomes an ally of the turtles, who try to help her locate her father.