You can also check out gears of war, ut2004 and ut3 as the way levels are approached in those is still identical to UE4. That way you have more reference and examples.
Ok, i have read all this thread, and lets see, @Hourences and @van Kuss
Despite of my bad english, i have understood that i need blender to make curved zones and areas. Well it is not FULL necesary, but it is the best choice for efficienty i guess.
So, for example, im in the way to practice, porting DM-Liandri from UT99, and i have this:
I suppose that i have to make this area on blender for the curved shape maybe? and then i can put a simple texture and then finish the rest of the map, and finally, at the moment of texturing the final version of the map, i must re-texture the mesh, right?
am i on the right way?
Lets install blender… 
thanks!
I think you’re right mate, when there are so many faces and that is clearly a curved corridor, you’d need a 3D model so you can import into the editor, it’s more efficient I think. I mean, it works like that too, but for a more professional look and a better performance meshes are better
Correct me if I’m wrong
Well you can make the shapes with Brushes. In fact the shape in the screenshot above shouldn’t be too difficult to do with brushes. But you are correct, it is more efficient to use static meshes to do it, plus you get more control over detail, uv’s, etc. But for initial blocking out of the level, then its fine to use brushes.