I just can’t download any app or make in app purchases!

Please, contact iTunes Support for that issue:

iTunes - Official Apple Support

Hm. Then try basic troubleshooting steps.

1. Make sure the Region of your App Store is correct under Settings > iTunes & App Store > Your Apple ID (you may be asked to sign in, if so enter your Apple ID and password to sing in) > View Apple ID and then tap 'Payment Information'. Now scroll down and find your Country/Region setting.
2. Head to Settings > iTunes & App Stores and tap your Apple ID and then Sign out. Sign back in.
3. You can also check if your payment info is correct on https://appleid.apple.com under the 'Payment & Shipping'.
4.  On your computer, open iTunes then, click Store and Account. This is your account page. Simply scroll down and find the 'Reset all warnings for buying and downloading' link and click Reset.

Come back with the results.