Cheolsu Saves the World 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

A massive asteroid is about to hit earth! Humanity has failed to stop a giant asteroid from plummeting into Earth, and life as we know it has ended. An ordinary Korean office worker named Cheolsu is somehow given the chance to go back in time and prevent this catastrophe from ever happening. Does he have a chance?