I redeem a 3000 gift card and when i’m making a purchase they asked me to enter my supposedly security question that I didn’t even remembered setting so my apple id is now locked and i can’t make any purchase
Apple id locked
try resetting its password (and then logging out and back in everywhere) : If your Apple ID has been locked - Apple Support
If that doesn't fix it contact iTunes Support and see if they can/will re-enable it : http://www.apple.com/support/itunes/ww or https://www.apple.com/emea/support/itunes/contact.html
If you've forgotten your answers to your security questions : If you forgot the answers to your Apple ID security questions