I cannot remember my iTunes backup password ! And I can’t turn off 2step authentication please help

Do you truly mean the old two-step verification?

Two-step verification for Apple ID

https://support.apple.com/HT204152

> "How do I turn off two-step verification?

Sign in to your Apple ID account page.

In the Security section, Click Edit.

Click Turn Off two-step verification.

Create new security questions and verify your date of birth.

You'll get an email confirming that two-step verification for your Apple ID is off.

If you mean the newer two-factor authentication:

Two-factor authentication is enabled by default on new Apple IDs and cannot be turned off. If you have an old account and recently activated Two Factor Authentication note this section of an Apple support article:

"Two-factor authentication for Apple ID" - https://support.apple.com/HT204915

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

... If you recently updated your account, you can unenroll within two weeks of enrollment. Just open your enrollment confirmation email and click the link to return to your previous security settings ..."

By the way, neither of these have anything to do with a true encryption of backups which is encryption of the backup files on a computer:

About encrypted backups on your iPhone, iPad, or iPod touch - Apple Support

As you can see, it helps to be very precise when asking about issues here and using exact terminology. :-)