Complex sentence: In 2012, Lee competed at his first European Junior Championships, he won the 3m Springboard gold and then went to compete at the World Junior Championships later in the season, securing a top result of seventh in the Group B Platform.
Split into simpler sentences: In 2012, Lee competed at his first European Junior Championships. He won the 3m Springboard gold and then went to compete at the World Junior Championships later in the season, securing a top result of seventh in the Group B Platform.