@elgolfo @thefabi
Depending how much time and motivation your friend has, there are considerations to make such as what should be the first priority.
Typically, ground level details would be the first priority such as POIs, street names, start and end house numbers of a street, etc with the focus of being able to navigate to the location.
Afterwards from bird view these details can be extrapolated onto larger items such as buildings, highways, or land-use.