forgot security question

See this Apple article: If you forgot the answers to your Apple ID security questions

If you forgot the answers to your Apple ID security questions - Apple Support

👉Scroll to Reset your security questions

1. Go to iforgot.apple.com.
2. Enter your Apple ID, then select Continue.
3. Choose the option to reset your security questions, then select Continue.
4. Enter your Apple ID password, then select Continue. 
5. Follow the onscreen steps to verify your identity. The information you’re asked to provide may vary based on your account details and other factors. If you don't get any options to verify your identity, you can't reset your security questions at this time.
6. Choose new security questions and answers and select Continue. See our tips for choosing security questions and keeping your account secure. 

After you reset your security questions, you might want to set up two-factor authentication instead. It's the best way to keep your account secure, and you won't need to remember any security questions. You can set up two-factor authentication right from your iPhone, iPad, or iPod touch with iOS 9 or later or your Mac with OS X El Capitan or later.

If you answer your security questions incorrectly too many times in a row, you temporarily can't use your security questions. Try to reset your questions after the waiting period ends. 

You can try the directions in this support article If you forgot the answers to your Apple ID security questions - Apple Support

but note that the article is labeled "archived" and may contain information that is out of date.

If you cannot reset the security questions then realize that several years ago Apple transitioned to using to two factor authentication instead of security questions. Apple has since been persistently encouraging users to switch to the newer security system and your only recourse may now be to try to change to two factor authentication as outlined in this article --> Two-factor authentication for Apple ID - Apple Support Follow the instructions in the section "Turn on two-factor authentication for your Apple ID"

If that does not work, contact Apple ID account security using the information in this document --> Contact Apple for support and service - Apple Support