Enchance documentations

I've been reading at the documentations recently (because sometimes I got bored :P) and tried to recall details of some of the issues I had. I added some that I think would be common for others.

More coming later if I could think of some else but I would like to get these merged first in case it might help.
the `integration` was a typo, should be `operation` but anyway, it's deleted now.