Anyway, about that impromptu,
in those patterns of 16th notes at the beginning, make sure you are not accenting the thumb, but practice slightly accenting the beat instead.
Try leaving out the first note (or just playing it by itself), and then playing the next four notes in a group, the next four in a group, etc.. quickly. Stop on the fourth note of each group.
da da da da da da da da da da da da da
this teaches your position changes to be smooth.
Other than that, make sure to shape each one of those arpeggios to whatever mood it seems to give. Each one of those is diffferent; this will make your playing much more beautiful.
Make sure to listen to the left hand, and know where it has the melodies, and bring them out.