Overall, the room was very clean and everything was there that we needed for a stay in Lisbon. Public transport (Metro and bus) is easy to reach to get to the city center and the airport is only 8 min away bar car (we took an Uber for just 4€).
We stayed at Maria's place for only one night as we had a stop over in Lisbon. I asked her if it's ok that we check in earlier as we landed in Lisbon in the morning and wanted to leave our luggage in the apartment so that we can use the rest of the day to explore Lisbon. Maria replied that an early check-in is not a problem and I should just send her a message once we're at the airport. We did so and drove to the apartment. Once we were there, we didn't really know where to ring, as there we no names listed at the house, so we tried to call Maria. We tried several times but couldn't reach her, so I left a couple of message on Airbnb, Whatsapp and sent a text, to notify that we would like to enter the building but were clueless where, when and how. As we had our luggage with us, we had to find lockers in one of the metro stations, which was overall a little bit of a hassle, as the city was crowded with backpackers who had the same idea.
Two to three hours later, I finally received a message from Maria on Airbnb (luckily I had data roaming) that we should meet her friend at the apartment later in the day. It was at first still not very clear how and when to meet her, as we tried to reach her friend on the phone but the number Maria gave us wasn't working.
We finally managed in the evening, after receiving more info from Maria (apparently she was traveling herself), to enter the building. We didn't meet her friend, but one of her two sons opened the door for us. He was very friendly and showed us the apartment.
I can see that a lot of people had a very positive experience with Maria, so I guess this was an exception in terms of check-in arrangements. I would still recommend this Airbnb as the place was very nicely decorated and cosy, however, the complicated check-in made our day in Lisbon significantly more stressful.