The Genius Grandson of Namgung Clan is a Manga/Manhwa/Manhua in english language, Action series, english chapters have been translated and you can read them here. You are reading chapters on www.mgeko.cc fastest updating comic site. The Summary is

Disaster struck ten-year-old Ha Hyeon, wiping out his entire clan. Having lost everything—his household and family—he barely survived and arrived at the Namgung family. There, he says to his maternal grandfather, ‘Sword Saint’ Namgung Muryong: “I don’t want to lose anything precious anymore.” Seeing Ha Hyeon’s determination to walk the righteous path despite his desperate situation, Namgung Muryong sends him to the entrance exam. There, Ha Hyeon begins to stand out with his remarkable achievements, learning and utilizing martial arts he’s never been taught just by observing. The heaven-sent prodigy ‘Ha Hyeon’ embarks on the righteous path to become the greatest under heaven as a ‘Namgung’!