why can i signed off from my mac ?

From this article:

Two-factor authentication for Apple ID - Apple Support

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

If you already use 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 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. Keep in mind, this makes your account less secure and means that you can't use features that require higher security.

There are 2 ways that I know

first one is going to Apple ID preferences and signing out from there

second is the remove your Mac from your account using a different device

No you can be I believe

you don’t always get a code

if so you can enter the login password for verifying instead

but I really suggest to use the passcode of iPhone or iPad because If your Mac has multiple users it’d be a pain

Can you give me a screenshot

I’m not sure on what you mean

That’s weird

Did you try the other way of removing the device

Just wait

when I removed my mom’s MacBook Air from my Apple ID using my MacBook Air it took so long that I decided to finish it on my iPad and it still took a few minutes