The main character has different personalities, one of them is an old samurai I think and the other is a salaryman who watched a lot of documentaries and stuff. Both personalities or people(?) are in the body of a young boy.

In the manga he made another source for sugar, made gold plated stuff, and a beauty product for girls hair and I think last I read he made a water pump. I remember quite a bit about it but not the name.

Could someone help me out?

Never mind I found it. To anyone interested it is called ISEKAI TENSEI SOUDOUKI