Hi there!
Learning how to use UE4 can be quite a difficult since it requires you to have knowledge in a wide area skill sets, it can be quite overwhelming! I’ll try to break things down for you.
The reason why your material looks different on your Mesh VS the Material Viewport is due to the UV mapping on the meshes. Your mesh is only displaying a section of your texture, making it look really stretched.
There’s 2 different solutions that you could do.
In Maya
- Change your Mesh’s UV in Maya so that it can occupy more of your texture space. A common technique for simple objects such as walls is to extend the UV past the bounds so that the texture will repeat.
In UE4 (recommended)
2. In your material set up, click on your TexCoord node and change the UTiling and VTiling to a higher number. Change it to something like 3 or 4, depending on what you’re after, that should fix it. What this does it changes the scaling of your textures so you can repeat or stretch a texture.
Some general tips with your assets!
In physically based rendering, your roughness should only be a value between 0 and 1. So I would recommend changing your Roughness value to something like 0.7. Generally you do not need a specular map in PBR apart from very specific situations, so I would recommend getting rid of that too, just leave the spec slot empty (leaving slots empty just leaves it at default values).
In terms of lighting a scene, I always put a Directional light and a Sky Light. Depending on your scene you might want to do baked lighting (static) or Dynamic lighting. Baked lighting is cheaper and tends to look nicer, so it’s good for showing off environments and stuff.
Hope this helps a bit! If you have any more questions regarding 3D modelling, Unreal Engine etc. I’m more than happy to answer them, good luck!
Oh and here are some documents to help you out:
https://docs.unrealengine.com/latest/INT/Engine/Rendering/Materials/PhysicallyBased/
https://wiki.unrealengine.com/LightingTroubleshootingGuide