How to use account recovery when you can’t reset your Apple ID password

You can use account recovery when you don't know or can reset your password

Use account recovery only as a last resort when you can’t sign in or reset your Apple ID password. 

After you start account recovery

After you request account recovery, you get an email with a confirmation of your request and the date and time of when you can expect to regain access.

• If you submitted your account recovery request with iforgot.apple.com through your device's browser, you should avoid using that device during this period. Using that device might cancel account recovery. 
• To avoid delays, turn off other devices that are signed in with your Apple ID until account recovery is complete. 

When the wait period is over, Apple sends you a text or automated phone call with instructions to regain access to your account. Follow the instructions to immediately regain access to your Apple ID.

See this link for reference

How to use account recovery when you can’t reset your Apple ID password - Apple Support