Please tell me if I am using the wrong feature as this is really my first attempt at creating anything in build mode.

I'm trying to build my own cinema because none of the ones I downloaded were what I wanted ... not exactly anyway. I'm trying to make one that resembles the cinema in my area and I can't find one with a large room where the movie is playing that has walkways on the left and right side that lead to the seating area.

Basically I want the building to be on ground level except a walk way that leads to the entrance to where the movie is playing which will be past the food area and the lounge, and a walkway in that room that leads down to the sitting area so you can watch the movie. However if I build the walk way inside the room first and try to make the ground level rooms afterwards it automatically gives it a foundation I can't remove and if I build the ground level stuff first then try to build a walkway it will give the entire building a foundation. I don't want that. Am I making sense or...?