The Reincarnated Prince Becomes an Alchemist and Brings Prosperity to His Country is a Manga/Manhwa/Manhua in english language, Shounen series, english chapters have been translated and you can read them here. You are reading chapters on www.mgeko.nl fastest updating comic site. The Summary is

Reborn as the third prince of a tiny and insignificant country, Hero happens to learn the forbidden-yet-powerful art of alchemy. Combined with his knowledge from modern-day Japan, Hero's abilities grow beyond what anyone in his world could fathom! With his newly-acquired powers, he’ll bring his country back from the verge of extinction...! A combination of modern-day knowledge and alchemy to turn a weak little country into a prosperous nation!