We can thoroughly recommend Jorn's place if you want to spent time in Berlin. Only a few steps to get into the ground floor apartment and security is excellent with shutters on all windows. A fruit & grocery shop is just around the corner as is the underground train station. It is very easy and inexpensive to get around and I recommend getting the Berlin Card. The apartment has an excellent washing machine that also has a drying cycle. It also has a small inside area for hanging clothes to dry should that be your preference. There were plenty of dishes, cutlery and glasses and a very good dishwasher. Washing liquid and tablets were supplied as was all necessary linen. Internet access is OK and certainly good enough for email and surfing the net. There is even access to Netflix should you have your own subscription (it's not provided free). The smart TV is linked to the network by wifi.
Probably the only criticism I could make is with the beds. For us (in our 60's) the beds were very hard and way too low. Getting out of them was a bit of a chore and we felt a little sore by morning. We got used to them, but would have preferred them to be of normal height. Other than that all was well. For the price you would find it hard to get a more functional and convenient place to stay.