The Schubert Sonata in B-Flat Major, D,.960 is one of the pinnacle pieces in the whole Western piano literature.
Learning the notes is one thing. Really understanding the music, and being willing to plumb the depths of this piece and incorporate this music into your whole being will be one of the supreme challenges of your life.
I am not exaggerating in the least when I say it helps to have experienced a life tragedy such as the death of someone you dearly loved, and also having accomplished something you wanted very badly, and having a spiritual/existential crisis which shook you to the very foundation of who you are and everything you believe to fully appreciate this music.
I heard this music for the first time when I was in my teens. I'm now nearly 60, and having been widowed, buried both of my parents and my partners' parents, and having been within a quarter mile of an EF-4 tornado (and survived!) I can now say I sort of have an idea of what this piece is trying to convey!
I'll give you a hint: Schubert's Piano Sonata in B-Flat, D. 960 is to piano music what Mahler's Ninth Symphony is to orchestral music!