Complex sentence: Eastman began wrestling with his older brother's junior varisty team, going on to dominate for the Merced High School wrestling team, went undefeated in his senior year and won the California State Wrestling Championship at the 191 pound weight-class.
Split into simpler sentences: Eastman began wrestling with his older brother's junior varisty team. He then went on to dominate for the Merced High School wrestling team, going undefeated in his senior year and winning the California State Wrestling Championship at the 191 pound weight-class.