If you can, change them at in your Apple ID Account https://appleid.apple.com/#!&page=signin. If you have been instructed to answer them and could not answer them satisfactorily, then Apple has notified you that we don’t have sufficient information to reset your security questions. In this case,
See If you forgot the answers to your Apple ID security questions https://support.apple.com/en-us/HT201485
You have indicated that you can't answer your security question satisfactorily. So see Security and your Apple ID https://support.apple.com/en-us/HT201303
This document says “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.”
Thus, given Apple's notification, we can do nothing to help you, except to mention that Apple support might help you if you have an extenuating circumstance (e.g., you have your receipt for your purchase of a pertinent device from an authorized Apple seller with its serial number on it). If you want to contact Apple Support to discuss any possible extenuating circumstance, see the support options below. Alternatively, if an Apple Store is open in your area, then you can go there to deal with your extenuating circumstance. You also can make a genius-bar appointment (https://www.apple.com/retail/geniusbar/) if you want.
Get a call from Apple support to help solve your problem using this link https://getsupport.apple.com/?caller=kbase&PGF=PGF63005&category_id=SC0245&symptom_id=23362
Apple ID Support https://support.apple.com/apple-id
Apple Support Twitter https://twitter.com/AppleSupport
Apple ID account security for country-specific and region-specific help https://support.apple.com/en-us/HT204169
Get Support: We’re here to help https://getsupport.apple.com/. Go through the options to find the best support option.
