Issue with styles

How do I make this into a section style? And I have things on the inside, why is it all black?

51H_SOUTH_Simplified14.skp (5.8 MB)

I don’t know what a section style is.
The reason it is black inside is you have section fill turned on. View/Section Fill

Any idea how I can make the floor fit exactly to the elevator?
51H_SOUTH_Simplified15.skp (5.8 MB)

Section planes are like pieces of geometry, you can select them and move them with the move tool. However, your section plane is not square with the face of the elevator/dome, so If you move it toward the elevator it will clip one side first. Because section planes are like pieces of geometry you can rotate the plane using the the rotate tool, then you can move it close to the elevator.