Hi yw,
You've been able to get this second movement into your fingers quite well to the extent that you can execute the score as you see (or memorize) it.
Yet this music is not so much about what you see on the staffs, as much as what you can only discern "between the lines" of the music where there is no musical notation at all; rather, it is about sensing the inner Rachmaninoff. This music is very ruminating, pensive, reflecting, and longing in its character. There is some deep emotion there--so as often occurs with Rachmaninoff, it has to be played from the inside out, rather than from the outside in. That's why it's so often difficult. At the moment it is being played more from the outside in. For you this will not come overnight at your tender age. (But enjoy being young, as you are only young once!

) This element of the lyricism in this piece will become much more apparent to you as you become more seasoned in the art of piano and interpretation. In the meantime though, you've paved the way for that day from what you've already accomplished in bringing the movement to this point. So when you gain new insights into the music, it will be quite easy to blend those ideas into your playing. Keep up the good work! I enjoy listening to you play.