How can I change the emailadress, the security answers of my apple ID are send to, if I dont remember the questions? Emailadress doesnt exist any longer! PLS HELP

Hi guys,

I need urgently help. I have a new mac and wanted to buy some goods out of the app store. Due to the fact that it would be the first buy on the new device, I have to answer some security questions (AppleID) I ve already forgotten! Now I can send the answers to a certain emailadress I have chosen years ago. But those emailadress doesnt exist any longer and I cant find a way how to change.

Can you help me and give me an advice?

Thanks a lot

Ian