Complex sentence: Viola and Shakespeare say their goodbyes, and he vows to immortalize her, as they improvise the beginnings of his "Twelfth Night, Or What You Will", imagining her as a castaway disguised as a man after a voyage to a strange land.
Split into simpler sentences: Viola and Shakespeare say their goodbyes, and he vows to immortalize her. They start to improvise the beginnings of his "Twelfth Night, Or What You Will", imagining her as a castaway disguised as a man after a voyage to a strange land.