You can use the data from OpenStreetMap. I don't know if you're familiar with the Overpass API, and I also don't know if that data from OSM is accurate.
One way of doing it is by using overpass-turbo.eu. After finding Podgorica, use this expression in the Wizard:
place=city and name=Podgorica
Build the query and Run it. You will get the city boundary as well as a point. You can get rid of the point if you delete the line starting with node. You can export the result as a GeoJSON in WGS84, which you can open in QGIS.
The same thing can be done in QGIS using the QuickOSM plugin.