I cannot purchase any apps. Anyone knows why? This will appear everytime i click buy " you may not purchase please get help from www.apple.com/support/itunes/ww/

You should do what it told you to do.

Contact itunes support

If you are getting a message to contact iTunes Support then you can do so via this link and ask them why the message is appearing (we are fellow users here on these forums, we won't know why) : http://www.apple.com/support/itunes/contact/ - click on Contact iTunes Store Support on the right-hand side of the page, then Purchases, Billing & Redemption