Knowing the notes better implies (at least what I think Chopincat was saying, correct me if I'm wrong) having the entire piece under your fingers, able to play through the entire piece with little to no mistakes in timing or notes.
- Relaxation is really of my concern. Each time speed rises, I'm unable to relax myself. And didn't find the solution to improve that. The worst example is for Fantaisie Impromptu, playing right hand alone : I feel tired before the end of the first part. Do I need time and repetition to improve that, or do I miss something working as I work now ?
That's exactly what I meant. Obviously you know the piece, but it seems like you are still making a few mistakes with timing and notes and aren't totally comfortable in every section. All of those things will improve with practice and time - muscle memory is an amazing thing.I can relate - I naturally hold a lot of tension in my shoulders, and it took a lot of practice and work with my teacher to learn how to deal with that. Being more relaxed when you play in general may be more of a long-term goal. But in this piece, there are definitely a few things you can do to overcome the tension in the B section. I remember that I used to tense up a lot in this section because I would stretch my right hand in order to reach all the notes. But stretching your hand out only makes your hand tense and restricts mobility. Eventually I figured out that it was much easier to keep my hand closed/relaxed when playing this section, and instead use my arm and wrist to move over the notes. That way my fingers were more relaxed and could move a lot more easily. That made it a lot easier to speed up! You should practice the right hand alone like this until it feels smooth and free. It won't be tiring if you are truly playing it in a relaxed way because you won't be straining your fingers. Hope that helps!