Kathrin was a great host during my stay, the room was exactly as pictured and the hostel is in an excellent location surrounded by all sorts of cool restaurants. She also let me leave my belongings in the room a few hours past the check out time. All in all, I had a wonderful time during my stay.
One thing to keep in mind: While Kathrin checked my proof of vaccination upon arrival, no one at the hostel was wearing a mask during my stay (April 2nd-3rd 2022 - Berlin Senate no longer mandated masks at this time). If this is the sort of thing that worries you, you should probably look elsewhere.