Mario's place is extremely comfortable, clean, and spacious. It has two separate bedrooms, so is suitable for two separate travelers (or a couple plus one), which few airbnbs offer. (Watch out! some of the hosts state that they have 2 bedrooms, when actually one bed is in the living room.) It also has 2 bathrooms, which is an incredible luxury in Berlin. Mario provided plenty of towels and a well stocked kitchen.
Even though Mario wasn't there, he made everything very easy, as he left the keys with a neighbor and he was always available on Whatsapp. We'll definitely stay at Mario's place when we return to Berlin.