I can’t buy things with Apple ID

See this Apple article: Payment methods you can use with your Apple ID

Payment methods you can use with your Apple ID – Apple Support (UK)

See the following Apple articles:

If you can’t download or update apps on your iPhone or iPad

If you can’t download or update apps on your iPhone or iPad – Apple Support (UK)

Require a password for App Store and iTunes purchases

Require a password for App Store and iTunes purchases - Apple Support

Go to this→If a message says 'Your account has been disabled in the App Store and iTunes' - Apple Support. There is a link in that article that will take you directly to iTunes support.