delete icloud account

I created an iCloud account (and also apple ID) with an iCloud email address.

Now I want to delete the iCloud email address (dmpjr5wpf18.cavani@icloud.com) and use my company address (giuseppe.cavani@lb-technology.com) instead as iCloud ID and Apple ID/Primary email without loosing the apps I bought on app store.

I tried to set my company email address as primary email address in apple ID but I can't save changes. No error i displayed. The addess seems to be correct (the three dots in the popup that shows up beside the address are green) but the page doesn't allow me to save.

Thank you.