I'm learning Chopin's Nocturne in C minor, posthumous. I think it's sometimes referred to as No. 20 and sometimes No. 21. I'm about halfway through and things are going very well, but I've reached a roadblock at measure 25. Can someone tell me how to play the series of nine sixteenth notes over the four eighth notes? I've been working hands separately, but all falls apart with hands together. I can see there's going to be a similar problem in measure 28. I don't have a teacher at the moment, so someone please help. Maybe it just takes a lot of practice, but if there's something else, I'd like to know it. Thanks a lot.