This is the 6308th most frequent Turkish word.
üzerlerinde
"On them" or "over them"
In this sentence, 'üzerlerinde' refers to the physical placement (on top of) the books.
Kitaplar üzerinde kalemler var.
There are pens on the books.
Here, 'üzerinde' is used figuratively to indicate focusing or concentrating on a subject (the project).
Arkadaşlar üzerinde çalışacağımız proje hakkında konuşuyor.
The friends are discussing the project we will work on.
In this context, 'üzerinde' signifies actions or changes related to the buildings.