Climbing the Tower that Even the Regressor Couldn’t 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 friend who passed out while drinking suddenly said something strange. “Suhyuk, I’ve regressed.” “Regressed?” “Yeah, I’ve returned to the past.” “Are you crazy?” “You’re the only hope left for mankind.” And so, he was dragged into the Tower, but… it doesn’t matter! Regressor? Tower? Trials? Whatever they are, I’ll conquer this damn tower!