For anyone that comes to this question, I have found the solution to be able to work with the Landscape module and all the classes related to it:
First you can read about the minimalist API of the Landscape API here:
This topic talks about the Landscape API being a minimalist so you directly access or create an object of the child classes.
So the way to use the child classes is by 
1- create the Landscape object using : ALandscape* land = Cast<ALandscape>();
2- using the land object you can get a reference of other classes by using the getClassname() method: example: ULandscapeInfo* landInfo = land->GetLandscapeInfo(); or ALandscapeProxy* proxy = LandComponent->GetLandscapeProxy();
In the proxy example we are using the LandComponent object which is a ULandscapeComponent.
For reference of the Landscape module:
https://docs.unrealengine.com/4.26/en-US/API/Runtime/Landscape/