I would certainly recommend El's apartment as a place to stay while discovering and enjoying Berlin.
El was responsive and very kind host. Her apartment is new, clean and spacious. It felt cozy and sunny even in December, thanks to huge floor to ceiling windows and underfloor heating system.
But what makes this apartment really special is it's location close to Berlin Mauerpark. We enjoyed a great view on Mauerpark from living room windows and, of course, visited a famous Mauerpark Sunday market. There is a grocery store in the same building that is open also on Sundays, which is very convenient. The adjacent district provides a rich selection of restaurants. We also enjoyed Christmas Market in KulturBrauerei, which is just 5 minutes walk from the apartment.