About Apple ID security questions
Click here --> https://support.apple.com/HT201363 to "Learn about Apple ID security questions, including how to set up or change your questions."
"If you forgot the answers to your Apple ID security questions" click here --> https://support.apple.com/HT201485
If you see the message "not sufficient information" see if at this stage you can still sign up for Two Factor Authentication:
Two-factor authentication for Apple ID --> https://support.apple.com/HT204915
If you cannot resolve the issue by signing up for Two Factor Authentication, "Contact Apple for help with Apple ID account security"; click here --> https://support.apple.com/HT204169