I stayed for one week at Daniel’s house and I really had a wonderful experience. Daniel was a very nice and helpful guy and provided me with everything I needed. He always spoke German to me and was very patient (I went to Berlin to improve my German). He was always ready to recommend me some places of Berlin to visit. Sometimes we had breakfast or dinner together, even once I cooked a Spanish omelette for both of us.
Regarding the flat, everything was wonderful. The bedrooms are very well isolated from the street and they had a very good equipped house and kitchen!! I definitely recommend to stay there!! I really had a wonderful experience.