Piano Forum

Neither of these is difficult.  To play mathematically correctly, that is.  To play musically?  Ah -- that's a different matter. 

In the first example, with the tie line, the idea is to place a very very slight accent on the 5th  sixteenth note of the left hand broken chord.  The sixteenth triplet in the right hand goes -- more or less -- with the last two sixteenth notes of the left hand, with the sixteenth note just before the triplet as a kind of pickup to the triplet (and it should be, musically, delayed a fraction after the 4th sixteenth note of the left hand).

In the second example, Take the basics first: you have the broken chord sixteenth notes in the left hand -- 12 notes, in two groups of 6.  The first note of each group should have a very slight accent on it, and the third and fifth in each group another slight accent (but less than the one on the first note of the group).  This give you the six basic beats of 6/8 time, by the way.  Then, in the right hand, starting at the beginning of the measure, you have a quarter note followed by and eighth; these notes match up with the six notes of the first broken chord in the measure.  Then you have the three eighth notes which match to the first, third, and fifth of the eighth notes in the left hand.

Now, and this is important at what I expect is your stage of learning the piece: Play it that way, in strict time, without the turn, until it is rock solid.  Once you have it so it is rock solid that way, you can introduce the turn which, as others have said, is F, E flat, D, E flat, starting exactly where the F started while you were learning it, and including the written F as a slightly longer note.  Mathematically you might think of dividing that written F into two pieces: the turn and the written F, of equal length, but it needn't come out that way when you play it -- the written F should be a bit shorter, starting slightly after, not exactly on, the G of the broken chord in the left.

How exact this is depends a lot on the tempo.  If it is slower, it will be more exactly half and half.

Whatever you do, keep that left hand on an even pulse.  Rubato in Chopin is very important, but must be used with a great deal of caution and is often overdone.  As far as left hand rubato in this -- and many other of the Nocturnes, which use the same general style -- the tempo variation in the left hand, if any, should be much more in the nature of a slight suspension in the last one or two notes of the broken chord, and never (in my not so humble opinion) in the middle or beginning of one!  In the right hand the importance is to make the whole thing sing; if it is necessary to stretch or note here and there -- and it is -- that is what you are striving for.