Julius has been very cool, described the neighbourhood and stuffs to see, places to go out. He was very flexible to give us the keys, whatsappable in case of any question during our trip...
The apartment is wide, clean and confy, we probably didn't explore everythings available inside it but we enjoyed the time we spent in it.
The neighbourhood is very calm... Not the most attractive in Berlin, but U-bahn and S-Bahn are very close (maybe 5 minutes away), you can be at Brandergurger Tor in 15-20 minutes, Warschauer Strasse in 15 min... And come home in the middle of the night easily and with no one bothering you...
We definitely recommend Julius and his apartment...