Olga's apartment is a gem among many other experiences I have had in past, It can be easily located if you use public transport or walk. I usually walked to the city center to just get a good feeling of the streets and life in Thessaloniki. The place is close to a supermarket and a few restaurants with local delicacies.
Olga is a very warm and welcoming host and we had great conversations on Greece and any other topics, she's very enthusiastic and shared very helpful information on how to get around and what to visit in Thessaloniki.