Hello brainspin, this note is independent of the changes made on the map with an editor. 

I did not look at the changes you had made on OSM. My focus was on the note.

After checking I noticed that the National Theatre building has been mapped with incorrect building parts (ie. overlapping parts with no indication about where each level starts).

The change you made is a good idea. It's what we refer to as Indoor Mapping [1] but with the way you've done it you have created another building inside the National Theatre.

I think it's better to hold on indoor mapping if we don't have a good overview of the floors in the building. It's better to avoid the chaos and let patrons find their way to the stages and other rooms.

1. https://wiki.openstreetmap.org/wiki/Indoor_Mapping