If you can't reset the security questions because there isn't enough information, contact Apple ID Support.
If you don't know the answers, if the steps in the article below don’t work, contact Apple ID Support, although I’m not sure they will be able to help.
Apple ID - If you forgot the answers to your Apple ID security questions. https://support.apple.com/en-us/HT201485
From the article below.
Without proof of your identity via security questions and other carefully selected criteria, Apple Support can't help you reset a password or perform any other actions on your account. These policies are audited and reviewed on a regular basis.
Security and your Apple ID. https://support.apple.com/en-us/HT201303
Apple ID - Official Apple Support. https://support.apple.com/apple-id
Contact Apple for help with Apple ID account security - Apple Support. https://support.apple.com/en-us/HT204169
Get Support https://getsupport.apple.com Work through the screens to get a chat option.
https://twitter.com/AppleSupport
Or fill out and submit iTunes Store - Contact Us - Official Apple Support https://support.apple.com/en-euro/itunes-contact The form is for iTunes, but it will get passed to the ID Support section.
