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.