Complex sentence: Before doing, boxing, he was just an island man who went along with the monkeys, therefore gaining superb speed and agility with Volg-san barely seeing him move from the corner in a sparring match.
Split into simpler sentences: Before doing, boxing, he was just an island man who went along with the monkeys, therefore gaining superb speed and agility. Volg barely even saw him move from the corner in a sparring match.