Andrija's apartment is a very good place to stay if you're looking for comfort and functionality. The place is not far from the center and is close to a lot of restaurants, pubs and coffeeshops. Public transportation is close by if you're looking to go a bit farther from the area.
While he wasn't there to show me around the apartment, Andrija was very responsive to any questions I had with check-in or the apartment in general through WhatsApp. Only problem is that there's no AC system in the place but that's not a problem if you're coming to Vienna in any other time of the year. Overall, it's a great place to stay in a quiet neighborhood.