I would like the floor to be separated so that each room has its own floor. The thick lines prevent this from happening. Please help me:)
The thick lines are profile edges. They aren’t preventing you from getting separate faces, they are indicating you haven’t done what is needed to make the separate faces.
There are a number of reasons why you have those profiles where you have them. Try tracing over the edges with the Line tool. Sometimes that’s enough. Sometimes there are gaps preventing closed loops of edges. Sometimes there are over runs of edges that need to be deleted, sometimes the edges are not on plane which prevents them from creating faces.
Upload the .skp file if you are still having trouble so we can take a look and sort out the problem.