Complex sentence: Boys' Doubles along with his Indian partner Sumit Nagal, defeating Reilly Opelka and Akira Santillan in the final becoming the first Vietnamese tennis player ever to win a Grand Slam trophy.
Split into simpler sentences: Boys' Doubles along with his Indian partner Sumit Nagal, defeating Reilly Opelka/Akira Santillan in the final. He became the first Vietnamese tennis player ever to win a Grand Slam trophy.