I stayed as a solo traveler at Nikolai's place for 2 nights, and it was perfect/ample for my needs. I was looking for a place close to the home of a family member, who walked me to the apt at night (after midnight). I didn't experience anything that made me feel unsafe. Note that the building door needs to be closed properly or the lock doesn't engage.
Check-in was easy, the apartment spotless and spacious, and the building quiet. Nikolai was quick to respond whenever I had a question and even arranged for me to be able to check in early, which I appreciated.
The window A/C in the bedroom let in some cold air and street noise, but I turned on the heater and used a white noise app on my phone and slept fine. I also used an eye mask.
The bathroom is narrow/awkward (there's a tiny sink on top of the toilet tank that runs cold water when you flush), but workable. There was also shampoo, a hair dryer, and a pitcher of filtered water in the fridge.