https://www.royalroad.com/fiction/20500/to-build-an-empire-revised For the revised version.
An architecture major, dies and is reincarnated in the lowest bums of society as a slave. He is born on a mysterious planet underground, working in the mines as he tries to work his way up the social ladder. Vying to become a power in the world, will Tylor Justifix rise from lowly slave to emperor of the world?

With his knowledge, he plans to carve out his own path and fix the problems presented to him in this world. In a world full of magical creatures, wizards, evil armies, and corrupt kings, Tylor stands up to them all with the hilt of his noble sword from another world.