Our stay at the apartment was perfect. Everything in Belem is easily reachable by foot, the city center can be reached by bus or train within 25 minutes. Uber is also pretty cheap.
The apartment itself was exactly as described, we had everything we needed. The church that can be seen in the pictures is not operating, so it's also extremely calm which is great.
We really enjoyed our stay and will definitely come back when being in Lisbon.