I loved this apartment! It was small and cute and super clean, in a freshly renovated apartment house with only 3 apartments, so you hardly hear or see your neighbours. Trindade is a great area to stay - it's more quiet and local than for example Aliados or Sao Bento areas etc, but still only few steps away from all the main places. Which is the most comfortable - Trindade metro station is just across the street and it's really easy to move around with a metro from there (all main lines have a stop there). Grocery store (Pingo Doce) is ca 5-7 min walking distance, some smaller fruit shops etc even more near.
And you have to try out local restaurant "Sai Cão" downstairs which Irene suggested - especially if you love freshly grilled meat or ribs (it has other good dishes also of course) - you will be surprised!
Wish you a nice stay!