The appartment was right in Gracia, a less trouristy area. Two subway stations are nearby. So it is no problem to get around. There are a lot of nice little restaurants and bars. I was happy to find out that they serve craft beer. Unfortunately I did not get to meet Silvia because I came one night later and left earlier than my friends. However, Silvia managed to hand over the keys in the middle of the night on a short noticed. She was very responsive and helpful via WhatsApp.
The rooms are very clean and the little court is just amazing to sit in in the morning.

There are only two minor downsides:
It can be a little noisy on Fridays and Saturdays until roughly 2am. However, I recommend to go to one of the three plazas nearby on weekend nights anyway.
At least our bed was roughly 1,80m. I did not mind but for some people it might be a little too short.

In any case I will be happy to come back.