Guten tag! My SO and I have been talking seriously about heading back to Berlin next summer for about a month. We used AirBnB for three nights there in May and stayed in Bornholmer Strasse. I know that there are whole-apartment options on AirBnB but I was wondering if there are companies that provide fully-furnished studio apartments that visitors can rent for short-term stays in Berlin? Something like Cityden in Amsterdam. I know it sounds a long way away but I am obsessed with predicting, planning and knowing (does that sound very German? haha..) Danke schoen!
You might check Berlin Habitat. Although he has been cracked down on and most of his holding require 2 month rentals now, he still rents two furnished std=ios at a great price in a building at the edge of the Mitte on the way to Prenzlaurberg. Great location, we stayed in one for a week in 2014 and were quite happy with it.
Have a look at the Adina Apart-Hotels. There's one in Hackerschemarkt and another near Checkpoint Charlie. Full apartments or studio rooms with cooking facilities but with hotel services too. https://www.adinahotels.com/de-en/hotel/berlin-hackescher-markt/?utm_source=googleplaces&utm_medium=organic&utm_campaign=googleplace
I can recommend Miniloftmitte, although be warned that the beds are Japanese-style futons, so avoid if you want something softer.
Accor has an Adagio Aparthotel there. Looks a little on the corporate side but IMO, that's not always a bad thing.
https://www.accorhotels.com/gb/hotel-7329-aparthotel-adagio-berlin-kurfurstendamm/index.shtml#!