The ingame map of the base is pretty much useless if you wanna learn out the routes and ''key'' places. I saw these maps in some walkthough video descriptions on Youtube and grabbed them to safe, as someone had done these manually and these are extremely helpful to understanding the Base + Necropolis layout.

Base: https://imgur.com/xfoE6A6

Necropolis: https://imgur.com/dhrQtO6

Someone propably would want to redo these manually to be better quality ones and more clear, but this is a good start.