Fix faulty lighting efficiently - HELP

It’s my second project with Unreal and apparently the lighting setup doesn’t work out:

Even though everything has the same material, the surfaces are rendered in the most different and unwanted brightnesses. Also, different meshes (on the image the facade vs sidewall/ceiling) are rendered in different shades.

The way I set it up was importing the (massive) geometry from 3ds Max as skeletal mesh, applying the same material to it (except for the floor) and setting up directional lighting coming into the room and a point light within the room.to support the light (though intensity in both cases is something that has yet to be adjusted).

My goal is an organic architecture with all meshes except for the floor becoming one fluid surface. How do I achieve this with a moderate set of skills and limited time (up to like 15 hours but I wouldn’t mind if it goes way quicker than that if not even by a few clicks)? Do I have to manually create lighting maps (if that’s even possible in this case since many surfaces are shifting around) or are there faster ways to tackle this?

Eventually, it is supposed to be a submission of an architecture project as a virtual walkthrough through an apartment where lots of elements (including the windows of the facade you see on the picture) are shifting. As always it has to look good but it doesn’t have to be a masterpiece, especially considering that it should be finished by Tuesday evening.

I would be really grateful for your suuport!

In case you wanna take a look at the file: Microsoft OneDrive - Access files anywhere. Create docs with free Office Online.