Can’t download any apps or games from the appstore

Enter valid billing information.

Change or remove your payment information from your iTunes Store account (Apple ID) - https://support.apple.com/HT201266

Payment methods you can use in the iTunes Store, App Store, and iBooks Store - https://support.apple.com/HT202631

If your payment method is declined in the App Store or iTunes Store [or you have a billing issue with a previous purchase in the iTunes Store] - https://support.apple.com/HT203005

If you still have problems,

iTunes [Store] Support - Use this form for assistance with account and billing, code redemption, or purchase questions -->

https://www.apple.com/emea/support/itunes/contact.html

or:

Contact Apple for support and service - "See a list of Apple phone numbers around the world." - https://support.apple.com/HT201232