I can only recommend Daniel's place!
The appartment is very clean and has a "new" feeling, the kitchen is fully equipped (oven/microwave, dishwasher, spacious fridge + separate freezer, washing machine/tumble dryer, ...) and the bathroom is nice too. It has a bathtub :)
The room is great, with a comfortable bed, big enough wardrobe, a TV screen and bright lights. I did NOT feel that the room was small, and it was perfect for a longer stay.
Supermarkets (Aldi and Penny) and two busses are very close neraby. The flat is 10 min away on foot from the central station, from which you have connections to all of Berlin as well as long connection trains to Germany and other European countries. Also, you can reach the airport Tegel (TXL) in half an hour, door to door!!
Daniel is very friendly person and a very helpful host.