I have forgotten the answer to the security questions

Read this about Apple ID security questions: Click here --> Change your Apple ID security questions - Apple Support to "Learn about Apple ID security questions, including how to set up or change your questions."

There's link at the end of that resource for a document about what to do "If you forgot the answers to your Apple ID security questions". However, it is to an archived document which typically means that Apple is no longer supporting features and services discussed in the document. Apple replaced security questions several years ago. You can still use them but Apple probably won't provide assistance resetting security questions and answers. Your option is to see if at this stage you can still sign up for Two Factor Authentication. Apple has been very strongly urging users for several years now to use Two Factor Authentication instead of security questions. "With two-factor authentication, you don't need to remember any security questions.

Click on this link for more information about 'Two-factor authentication for Apple ID' --> Two-factor authentication for Apple ID - Apple Support

If you cannot resolve the issue by signing up for Two Factor Authentication, "Contact Apple for help with Apple ID account security"; click here --> Contact Apple for help with Apple ID account security - Apple Support