For a first experience in Lisbon, I would definitely recommend this place : we were 6 and the flat is big enough for everyone and it's has an amazing view on the terrace on the square.
It's very well equipped with any kitchen appliances you might need, and it's location near all the best spots in Lisbon (we didn't walk more than 15min to reach our destinations).
Aside from the apartment, we had great help and support from The Conciergerie, who help us quite a lot organizing the activities for our stag party (Special thanks to Paulo and Francisco).
Again awesome place👌