Serafin's apartment is very nice, but we had a few communication issues throughout our stay.
I had to ask a few times for parking instructions, and the ones I received were unclear. We were asked to notify the host's colleague 40 min before our arrival so she could meet us at the apartment, but she wasn't there when we arrived. After waiting for 10 min or so, double parked in the street, I called her, and found out she doesn't speak English or French (the languages listed on my profile). Eventually another colleague of the host arrived to let us in and show us around the apartment, and while he was very nice, he did not speak English or French either. It left us feeling a bit unsure of how to use certain appliances, etc.
A couple of days into our stay, we returned to the apartment in the evening and noticed a few signs that someone might have stopped by while we were gone. We weren't sure until the next morning, when we noticed the WiFi router and info had been changed. I contacted the host, and he apologized and said he thought his colleague had told me she was coming by with a Vodafone technician. We would have been pretty uncomfortable that someone had let themselves into the apartment without our permission even if we WEREN'T in the middle of a pandemic -- we had to spend time checking that none of our belongings had been touched or taken, and after we confirmed that people HAD been inside the apartment, it was far too late to ensure everything had been re-disinfected. Serafin confirmed a few days later that it was.
The apartment itself is very spacious and well-equipped. The dishwasher, washing machine, and dryer are a great bonus. The location is convenient to the city center and the old town, and it was great to have parking included (our friends who live locally said parking can be difficult to find and/or very expensive in Bilbao).