I stayed at Wohnung mit Spreeblick direkt am Ostkreuz for almost 3 months during the pandemic (including 1 month of full lockdown), as I was working on my new start-up in Berlin. This was my first time in the city, and Fabian was very helpful in setting a flexible arrival time, showing me around, making sure the place is clean and everything works, as well as giving me some tips about living in Berlin in general.
The apartment is perfect for times like this, with spacious living room, kitchen and balcony making for a comfortable place to isolate, if you have to do it. While the internet is not the fastest, it was good enough to work and have video calls. The peninsula on which it's located is very calm and quiet, pretty much all residential, with plenty of walking and cycling paths and enough cafes & shops to live comfortably. It's also in range of all delivery services (Gorillaz, Lieferando, Amazon, etc.)
The apartment is also perfectly located between Ostkreuz and Treptower Park S-bahn stations, from which you can get to anywhere in Berlin within 20-30 min (including BER Airport and Ostbahnhof for long-distance travel). It's also a 30 min walk from Factory Gorlitzer Park.
I'm very happy with my stay in Berlin, and this apartment in particular. It was a pleasure and I can definitely recommend it to anyone visiting, even in these tough times :)