cannot remember the answer of my security question

You can reset the answers to your security questions, if you at least know your AppleID password.

See this guide on how to do it: If you forgot the answers to your Apple ID security questions - Apple Support

If you do not know your password or do not have a recovery email address, and none of the options to verify your identity suffices in your case, and waiting and trying again the next day does not help, you have to contact Apple Support personally. This page lists the different options on how to contact Apple for Help with account security problems: Contact Apple for help with Apple ID account security - Apple Support

Use the contact information for your country.