You can't beat the location of Nadja's place- it was the perfect base for our just over a week long Berlin trip. Walking distance to U and S trains, a huge variety of delicious restaurants, cafes and bakeries on your door step, a vibrant neighborhood, grocery stores within a couple of minutes etc.
The place itself was huge. I wasn't expecting it to be so large but it would easily accommodate 6+ people. I was really surprised at the size for the price and it was very welcome as you don't feel on top of each other- there is enough room to be comfortable and have space.
One thing really worth noting is all the beds are actual real beds, unlike a lot of Airbnb listings where a sofa is listed as a bed. There are 2 bedrooms, one with an enormous king size bed and the other with double sized bunk beds, as well as bunk beds in the living room that serve as a place to sleep and/or use as a couch/general seating. There is also a separate kitchen and of course the bathroom.
You need to be mindful that this is someone's home and you will be staying amongst their personal items. The flat is quirky and fun and we were respectful of the host's personal items. We used the kitchen for breakfast and coffee and it is well equipped but please note there is no microwave, electric kettle or toaster (no big deal for us, we used the grill to toast and the regular kettle for coffee).
Nadja doesn't charge a cleaning fee so asks you to change the beds and do a tidy before you leave which I think is really fair given the price. She provided all the sheets etc. so it only took a few minutes to swap everything around.
The only niggle I have about this place at all is that it was a bit chilly at night and we couldn't get the heaters to turn on. That said, I would (and hopefully will!) happily return to Nadja's home. We enjoyed our stay and found the flat had everything we needed and then some.