How can I deactivate the two factor authentication on my I phone 11

That 2 week thing does not apply in my country and may not apply in yours.

In UK you can create an AppleID (like to post in this forum) without any 2FA but as soon as you associate an Apple product with it the 2FA is mandatory and permanent.

You cannot back out, it is essential for all Apple transactions from signing in to buying apps and storage.

This is the excerpt from the article in blue st the top of this page.

”Can I turn off two-factor authentication after I’ve turned it on?

If you are already using two-factor authentication, you can no longer turn it off. Certain features in the latest versions of iOS and macOS require this extra level of security, which is designed to protect your information. If you have recently updated your account, you can unenrol within two weeks of enrolment. Just open your enrolment confirmation email and click the link to return to your previous security settings. Bear in mind that this makes your account less secure and means you can't use features that require higher security.”

I never got any option when 2FA came in some time ago, and when my wife bought her first iphone this year she never got any email, Did you?

If used for more than 2 weeks, you can’t.

Also bear in mind the 2FA is a feature of your AppleID, not the phone.