I can’t reset my security questions

You need to ask Apple's Account Security team to reset your security questions. To contact them, click here and pick a method; if that page doesn't list one for your country or you're unable to call, fill out and submit this form.

Contact Apple Support: Contact Apple for help with Apple ID account security

However, according to Security and your Apple ID:

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.