If he could explain us, where should mezuzah be affixed by the entrance of an elevator in the multilevel building? The door of the elevator opens inside the wall (and does not turn around) Is there difference between floors of the building?

There is more than one opinion on this issue. The Responsa Minchat Yitzchak (4, 93) holds that the elevator itself requires a mezuzah from the inside and not in the entrance of every level. Others require a mezuzah on the right side of those who enter the elevator apart from the main entrance of the building in which the mezuzah should be placed on the right side of those leaving the elevator. (Chovat Hadar p.43) Some exempt the elevator all together from a mezuzah. (Be’er Moshe 2; 88, 90) The last opinion I found is to place the mezuzah in all levels on the right side facing out of the elevator. (Pitchei Shearim p. 190) Most elevators I have seen do not have any mezuzah and those whom have, followed the last opinion above. (though I haven’t seen many buildings in religious neighbourhoods…) In any case because of the doubt the mezuzah will be placed without a Brachah.