According to the news page for Magellan Bookstore translated via google:
05/20/2016. Bookstore MAGELAN the requirements of its users will not
close the door during the summer season. Bookstore will operate at
full capacity during the summer months of July and August.
The store sells books in English and Serbian:
Magellan Bookshop is second-hand bookshop based in centre of Belgrade,
Serbia. It is probably the only second-hand bookshop selling titles in
English language continuously in this part of the world. It has great
selection of books, in Serbian and English, especially in areas of:
biography, travel & exploration, classics fiction, literary criticism,
art, religion, philosophy, psychology and history. Opening times:
Monday to Friday 12-20, Saturday 10-14.
There is a google streetmap view from 2013
антикварница appears to just be an antique shop according to a web search, rather than a second hand bookstore. I'm afraid I'm not sure what the correct translation should be.