Catarina and Antonio made us feel extremely welcomed! Their apartment is very cute, spacious enough. We (two people) stayed an entire week and we very much enjoyed it. There are two bedrooms - spacious, clean and both with a small balcony space you can step onto.
There was a booklet of recommendations that was prepared by Catarina and Antonio - restaurants, places to see, bars... you name it.
There were enough kitchenware that you could even cook meals if you wanted to... but don't. Food is cheap and delicious in lisbon!!! I personally really enjoyed Royale Cafe (in Bairro Alto).
This is a very convenient place to stay - you're right in the middle of all the places you should see in Lisbon and also great for public transit too. Close from the Rossio square where a lot of the subways, trams, are. I think the closest subway station is Martim Moniz though.
Make sure to check out Cascais. This is around 30 mins by train from Lisbon and is a beautiful place to see with beaches and cliffs. I went here twice in one week!
Also go to Bairro Alto for dinner + night life. There are lots of bars and live music and lots of energy even at night.

I spent an entire week in Lisbon + surroundings (Cascais, Sintra, Cabo da Roca) and I absolutely loved it and wish I had more time.
There is a lot to see and you won't regret it.

Thanks Catarina and Antonio!!