Complex sentence: She tried to protect Reyna while she was younger, they went to Circe's island because Hylla wanted to protect Reyna from the war, however, after it's destroyed, Hylla learns how to fight and fights hers and Reyna's way out of the island.
Split into simpler sentences: She tried to protect Reyna while she was younger--they went to Circe's island because Hylla wanted to protect Reyna from the war. However, after it's destroyed, Hylla and Reyna learn how to fight and fight their way out of the island.