Hey Shingo.
I can suggest that perhaps you leave that Beethoven one for a later stage. The thing is: Beethoven is known to be the most difficult pieces to play from the classical-era. I downloaded that specific piece recently and came to the impression that it has very deep emotional messages that one must bring out of the music. If you're going to struggle tecnically, you will have problems to paint the bigger, but detailed, picture of the piece. That won't give you any self-satisfaction. With Beethoven you can also perhaps adopt a slight romanticist-mindset, as he ends the classical period. But remeber to retain the feminine touch the classical era requires. For example you MUST play the first part of the moonlight SOFTLY. I'm male, and I sometimes tend to play hard, already on the first page.. carefull.
Regarding your second question: Be sure to set very certain, but realistic, goals as to when you want a piece to be finished. This helps, because you WANT to get it finished. Sometimes it is'nt bad to linger on the first part, because it prepares you emotionally for the rest that is to come.