How to off two-factor authentication for Apple ID?

See -> Two-factor authentication for Apple ID

Two-factor authentication for Apple ID - Apple Support

• If you're already using two-factor authentication with your Apple ID, you can't turn it off. If you updated to two-factor authentication inadvertently, you can turn it off within two weeks of enrollment. If you do, your account is less secure and you can't use features that require a higher level of security.

Read this paragraph:

"After you turn on two-factor authentication, you have a two-week period during which you can turn it off. After that period, you can’t turn off two-factor authentication. To turn it off, open your confirmation email and click the link to return to your previous security settings. Keep in mind that turning off two-factor authentication makes your account less secure and means you can’t use features that require a higher level of security".

Extracted from this support page:--> Manage two-factor authentication for your Apple ID from iPhone

Regards

Giulio