oh I know, but i would use it to jog it into my memory that bor=reside, while lever= live. I believe "Which floor do you reside in?" would fit better. Everything makes much more sense to me when it is directly translated most of the time (Unless it is complete and utter gibberish in english and in this case while it might be odd it still works). Tusen takk.
Although often used in spoken English, "What floor do you live on?" is actually improper. "Which floor do you live on?" is better, and to be completely proper it should be, "On which floor do you live?"
(You will seldom hear the last one spoken in America, but it is more common in the UK).