i forgot my security question what should i do

To change security questions: First, you need to know your apple id email and password. Without that this won't work.  Go to iPhone or iPad, go to settings > mail > accounts > add account> choose icloud> enter apple id email and password. It will then ask you to enable 2 factor? Choose 2 factor. After that it will use your phone number to verify you and will no longer use security questions. (Note you need to choose iCloud even if its a third party email.)