Complex sentence: He attended Hollywood High School studied art both in America and England during his teens and 20s, it was the American Southwest and the Hopi and Navajo tribes that defined his artistic body of work over the course of his life.
Split into simpler sentences: He attended Hollywood High School and studied art both in America and England during his teens and 20s. But it was the American Southwest and the Hopi and Navajo tribes that defined his artistic body of work over the course of his life.