We had a lovely time at Karsten's apartment. It's beautifully furnished in a mid-century style, clean and very well located, next to the metro station and very easily to get to the city center. Though we couldn't meet Karsten (he was on a trip) he gave all kind of facilities and tips to get to his apartment and he arranged everything, so a friend of him welcomed us and showed us everything. We fully recommend his place to anyone.