I have credit but I can't bye an app

What happens when you try to buy something, does the 'buy' button not work, do you get any error messages ... ? I'm not sure what 'can't continue in payment information' means.

If you are getting a message to contact iTunes Support then you can do so via this link and ask them for help (we are fellow users here on these forums, we won't know why the message is appearing) : 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

If it's a different problem ... ?

Is it a new account that you've just created ? If it is then did you follow the instructions on this page, for creating an account without giving credit card details, when creating the account : http://support.apple.com/kb/HT2534 ? If not then you will need to provide a valid payment method for your country.

That screenshot (which has your id on it at the top left, you have 15 minutes from time of posting to edit a post) has in red letters that you need to contact iTunes Support - you can contact them via the link that I gave in my first reply to ask why you are getting the message

See my reply above - you have a message, in red, on that screen to contact iTunes Support, so you will need to do so, we won't know why you are getting the message

I don't know what you mean by 'popular address', but the address that you have on your account should be your address.

You can contact iTunes Support via the link that I gave in my first reply.