Andreas is very nice person and everything worked out well. The "apartment" is a small but neat room. Very functional and clean with a central location. The window is to a small back area, only concrete and some trash to see. It's good for 1 person or 2 if you only use it for sleeping. It's most of the time extremely quiet, but sometimes in the morning your hear the neighbors pretty loud as the soundproofing is not very good. In case Andreas apmt is not available, check out the Astoria hotel. I had to stay another day and Andreas had already a reservation. I found on booking. com the Astoria and got a vey nice single room for Euro 24. Thessaloniki has an interesting nightlife, and with bus 45 and continuing to the outlaying beaches makes for a real nice day out.
But better just go out to Chalkidiki, there are plenty of rooms everywhere.