how do i change security questions?

Hi

If you set a rescue email address, you can reset your security questions yourself. Follow the instructions here to check whether this option is available to you:

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

Otherwise, you will need to contact Apple Support. Contact information is available here:

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

(I'm afraid that no-one here can resolve the issue for you. You are not talking to Apple here - this is a user-based community).

If you have forgotten your security questions and have supplied a rescue email when setting up your account, you can reset them at My Apple ID > security > Reset your security questions, otherwise...

Welcome to the Apple community.

If you are unable to remember your password, security questions, don’t have access to your rescue address or are unable to reset your password for whatever reason, your only option is to contact Apple ID Support, upon speaking to an operator you should explain that your problem is related to your Apple ID, this way you will not be charged for assistance, even if you don’t have an AppleCare plan.

You will need to show patience with the procedure and be prepared to demonstrate without question that the account belongs to you. Don’t expect access to be restored immediately and if you aren’t the owner of the Apple ID registered to the device the account won’t be reset.