How do you beat Super Mario sun shine?

You have to complete the Shadow Mario missions (Always mission 7) on all of the main stages. Then, you have to defeat Bowser at Corona Mountain.

It's too HARD!! GAAAAH!!! Pwn Shadow Mario ( who, BTW, SUCKS!!!!) on all mission 7s, pwn Bowser the Lowser, whos a loooooosa, get the shines and save PEEAACH.