Is there a manual for the game. There are things not really well explained in help and I want to know if there is a manual with more information regarding buildings and overseers.

Just get the manual of the original game. Nothing changed between the two versions, except if you enabled some custom gameplay options, like the recruitment system or the workers population. Also the RTS part is no longer present.

https://tinyurl.com/4aehj4mn

But i agree. The ingame help is a mess. Not only it's incomplete, but lacks a simple search box.