Before i begin i'd just like to say hello.
My names Benjamin Bielski
I'm 15 years old and i have played Piano since i was eleven.
Sometimes i feel annoyed because theres so much competition. I like to think im top in my area, (invercargill - NZ) but it annoys me that i didnt start earlier on.
I practise for about 2 hours a day now, but i started with about 30 min a day when i was 11.
I am classically trained, and hope to pput on some recordings and compositions of mine for you guys
Im currently working on two works, Debussys Duex Arabesques (Easy, but can be played to sound amazing)
And Beethovens Moonlight Sonata

The trouble comes with moonlight.

Now, In my opinion (and no disrespect intended) the first two movements are piss easy
But number three annoys me

I can play it. But i cannot maintain it.
My wrists gives up in the semiquaver bass with the G sharp octaves.
IS there any advice to strenghten my wrists??

Also

I often experiance back pains when playing
ANy advice???

My advice would be to not try to "strengthen" your wrists, but to relax them as much as possible. Pay special attention to any tension in your wrists while you're playing, and concentrate on relaxing that tension away. If you can't play it without tension, then try slowing it down some until you get control over the tension.

The relaxation technique might help with your back problems too. If not, try experimenting with bench height and distance from the keyboard.

Like Terez said, minimize the amount of tension in your wrist. My hands used to get tired within 3 minutes when playing this piece, so I started to play it a bit more slowly, so that I could relax my hands and wrists: Do not start off practicing that part at the indicated tempo, even though it's not difficult. First learn to get rid of the tension and then start to play it faster and faster. Once you get the hang of it you'll have no trouble playing this piece.

Thanks ill be sure to try that