I Won the Lottery and Went Back in Time!?!

He beat the lottery. Then he bought a time machine?!?! Leon Ren Falkner planned to return to the year 2000 and build the perfect life. Instead, one wrong selection sent him to the Synchronozoic Era; an impossible world where dinosaurs, mammoths, giant insects, and human tribes coexist across the supercontinent of Omniterra. His body was rebuilt. His time machine became a powerless cube. And getting home will require far more than survival. To recharge its temporal core, Leon must transform scattered tribes into a civilization capable of agriculture, medicine, metallurgy, chemistry, industry, and electricity. But he is not the first modern man to reach Omniterra. The machine seller’s missing grandfather is still alive, and the civilization he created may be more dangerous than the prehistoric monsters outside its walls. — Description from novelcodex.org