Weird texture and black shadows

First of all, sorry - my english is what it is, because I’m still learning.

Why my lighting in my map is so weird? Before building lighting textures looks fine and walls cast shadows. But when I press “Build Lighting Only” everything is weird and not working. Texture on one of the object is totally broken, shadows on the walls are completely black and there is not casted shadows on the floor. You can see what I mean on the screenshots. What’s going on here?

The slab on the ground is broken because you need to look into adding an additional UV set for lightmapping. For the dark wall check the display settings and see what quality it is set to.

Of course I did second UV for lightmapping. Both ocjects are made in UE4 from BSB converted to static meshes. The same as here: Quality for the wall is set to 64 (printscreen) if you mean that.

I found that something is wrong with UV Channel 0. Should it look like this?

EDIT: Ok, now I know what was wrong here. I found solution here:
Lightmap was not selected. Thank you for help.