Well, I mean old school style maps (with half-life/quake/doom etc. esthetics).
I tried inside UE and frankly, it’s very frustrating, resulting nowhere.
External DCC apps, like blender, seem too complex and there is a lack of online tutorials about this subject.
Any suggestion on how should I approach the matter?
Hi Dimer,
I never thought I’d hear “lack of online tutorials” and “Blender” used in the same sentence! 
I’d give the built in Modeling Mode a try. There’s also the cube grid tool that could be used to shape some old-school styled geometry.
As for the textures, to get a pixelated look: Open the Texture and set the Texture Group to “2D Pixels (unfiltered)”
Get lyra example, watch tut like this:
Or use blender to make meshes.
Or get some set of modular meshes from marketplace.