frida1 -
This is a beautiful Nocturne, well worth the (considerable) effort required to master it. One of the difficulties is sustaining the "long line" through the whole piece. Listen to as many recordings as possible. Ashkenazy does a fabulous job on this one. The RH trills with melody notes section is tough at first. Try measured trills, writing in the fingering where a trill note and melody note coincide. For example if you are trilling even 16ths with 1-2, write in whether 1 or 2 is coinciding with each melody note. Chopin actually stated that he was more concerned with evenness than rapidity in trills. Hope this helps, and good luck!