Read these:
About Apple ID security questions - "Learn about Apple ID security questions, including how to set up or change your questions."
https://support.apple.com/HT201363
If you forgot the answers to your Apple ID security questions - https://support.apple.com/HT201485
Security and your Apple ID - https://support.apple.com/HT201303
"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."
With that in consideration, if the online option does not resolve the problem try the general support link. I suggest trying to get a personalized response from a chat or telephone call. To do this, choose any topic, continue working your way down options until you get the desired form of contact, then ask to be redirected.
Contact Apple for support and service - Apple Support --> https://support.apple.com/HT201232
Apple is encouraging users to use Two Factor Authentication instead of security questions. --> https://support.apple.com/HT204915