Alien Invasion? Let Me First Teach the First Emperor How to Build Mechas

My name is Lin Jie, and I was born in the era of catastrophe on the earth. It was the darkest era. The earth was facing five civilizations that were far higher than the earth at the same time. Under the catastrophe, the only thing the earth could do was steal and survive. We stole the battleships and mecha data of the galactic civilization, stole the anti-scientific methods of alchemy and cultivation of the cultivation civilization, and infiltrated the Zerg in exchange for their genetic technology data at a huge price... However, despite this, the earth still failed. I died in the last battle of the earth's defense. As a super mecha master, a cultivator of the Void Refining and Harmony, and the last commander of the Longxu Army, I died in my hometown. However, what I didn't expect was that I traveled through time, took the system with me, and traveled to before the disaster. The farmhouse connected to the steel mill in my home welcomed batches of strange guests. I knew that the opportunity to change everything had arrived. Alien invasion? Don't panic, please allow me to teach Qin Shihuang how to build mechas first; teach Wei Zheng of the Tang Dynasty how to slay a dragon; teach Wang Xizhi how to draw talismans; teach Zheng He what a galactic battleship that can sail to Andromeda is... This novel and its characters are purely fictitious. Any similarity is purely coincidental and should not be imitated.