I stayed in the apartment for four nights with my 15 year old daughter - she slept in the bedroom on one of the two single beds in that room and I slept on the sofa bed in the lounge/kitchen. Access from the former to the latter is through the bathroom.
The keys were left for us in a small 'safe' by the front door to the apartment block and Brit sent us the code and access instructions to the flat in good time before we left.
The flat was well equipped for a short break and very clean. It is also well located with all sorts of shops, restaurants, cafes and so on a short walk away. Train and underground stations are also nearby making it easy to travel to different parts of the city - a Welcome Card travel pass would probably save travellers money.
We visited the 'must see' Reichstag - book online for tours before you go (I unfortunately didn't) - Brandenberg Gate, Memorial to the Murdered Jews of Europe, the Topography of Terror Museum and the East Side Gallery at the Berlin Wall. We also did a bus tour and a cycle tour with an excellent guide from Fat Tire, based at Alexanderplatz. The cycle tour was superb and I would thoroughly recommend it.
I would happily stay at Brit's apartment again - and recommend it to anyone using the AirBnB website.