I don't know the school system in Portugal and I don't know how old you are, but my first advice is this:
try to find a way to keep both options open as long as possible. I was in a similar situation in England in the 70s, with a choice between maths and music. I chose to do maths and science A-levels but continue studying piano and cello at the Junior Royal College of Music. Do you have a similar possibility in Portugal?
To help you with your reflections, here are my views on the two possible choices you mention.
1. It is insanely difficult to become a concert pianist. You need to basically dedicate your life to practising, and that is no guarantee of success. There's only a handful of pianists in the world making a good living out of solo concerts. Here's a documentary you should watch:
However, there are many other possible paths in music: teaching, or becoming a répétiteur for opera, for example. You wan't become rich like this, but it can lead to a rewarding and varied life for somebody who is so passionate about music that they want to spend most of their time doing it.
2. If you succeed in studying as a surgeon your are assured of a life in a high-income bracket. Even if you don't finish surgical studies, you will be well-prepared for many other jobs that require maths/science knowledge. Bear in mind however, that surgery is extremely stressful and
surgeons are highly prone to depression and suicide.
Hope this helps. Don't let yourself be pushed into a decision too early!