Saikyou de Saisoku no Mugen Level Up 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

Makoto Sakura, sixteen years old, finds himself without a place after dropping out of high school. Suddenly, an otherworldly relic appears before him. On that day, dungeons began to appear all over the world. Humans acquired a level system that completely overturned their previous values. Amidst this revolution, Makoto finds his place inside the dungeons. Acquiring cheat skills like “Experience Points x1000” and “Level Free,” he becomes a level 10,000 powerhouse. As the strongest “Player,” he embarks on dungeon exploration!