Hi there,
I see the problem you are having with Fur Elise.
After the rising triads in A minor (like small arpeggios), you then have to start a
descending chromatic scale - this includes all the white & black keys, moving downwards by a semitone. This is the bit you are having trouble with.
The main problem you are having is your fingering - it is all wrong!! (sorry)
You will never be able to play it with just one finger "up to speed"
Here is what to do....
Every time you go down from a white key to a black key (eg A - Aflat), use your thumb on the white key, and then cross over your 3rd (middle) finger onto the black key - always use your 3rd finger on every black key, no matter what.
Practise an exercise first, starting on any B (using the 3 black notes first)
So play (downwards) - B - Bflat - A - Aflat - G - Gflat (stop on Gflat for now), and use fingers 1-3-1-3. - remember to cross your 3rd finger OVER your thumb each time.
Now,,,, whenever you get to "two white notes together" - (eg F - E, or C - B), use your 2nd finger on F/C, then your thumb on E/B.
The descending chromatic scale should be 'legato' (smooth) and evenly played as triplets.
To help you further with these exercises, the chromatic scale starting on D is introduced into the ABRSM Grade 2 scales, arpeggios & broken chords book (blue cover) - I would recommend you bought this first, and check out the fingers for each note.
When you play an ascending chromatic scale, use fingers 1 - 3 from white to black, and 1 - 2 from white to white. Practise SLOWLY though!!
Hope that helps. Are you having piano lessons, or are you self-taught?
(Just for anyone's info - this is just for the right hand only in this piece, the left hand is resting)
Cheers
Colin