Our stay at Matthias' house exceeded our expectations.
The flat was amazing (spacious, bright, clean, with great autumnal view) perfectly located (minutes away from 2 tube stations, by the wall and the museum, walking distance to amazing bars, restaurants and breakfast places).
And Matthias himself was an amazing host exceeding expectations as well; attentive making sure we had all the info we needed to find the flat, providing advice and guidance about our stay and the city; even provided breakfast material (fully stocked fridge!!!).
Would definitely recommend a stay here both for the flat and the host as they both contributed to us having a great time in Berlin.