What a beautiful, spacious apartment! it's very well put together and comfortable. Carla is wonderful, so sweet, and communicative. We stayed for a month and worked remote there. Internet worked great, we had plenty of space to spread out. My parents came with us to help with our baby girl, so having multiple rooms and space was crucial.
A few things to note (that are clear in the listing but I feel are worth stressing for those who read through reviews): the stairs up are no joke (4th floor in Europe but really 5th floor for those of us from the US haha) and there is no AC which I'm sure usually is not an issue because of the big beautiful windows and balcony doors, but we were there at a particularly hot part of May (Carla graciously bought a fan so we wouldn't melt).
The apartment is close to the metro red line (direct to airport, SO convenient) and blue line (right into downtown/old town). And it's well served by multiple buses which were sometimes easier as we had our one-year-old in a stroller and some stations don't have elevators. It's in a nice courtyard and close to many, many restaurants and a couple handy grocery stores.
Overall, we loved our time in Lisbon and having a nice place to work and stay was wonderful! if you need space/multiple bedrooms, this is such a great place!