Complex sentence: His technical background found its roots in the Tae Kwon Do, his first discipline, where he got a black belt, that he soon overcame to dedicate himself to the practice of Kickboxing and Muay Thai.
Split into simpler sentences: His technical background found its roots in the Tae Kwon Do, his first discipline, where he got a black belt. He later dedicated himself to the practice of Kickboxing and Muay Thai.