According to Facebook Support Center, it may take up to 90 days from the beginning of the deletion process to delete all the things you’ve posted. While Facebook deleting this information, it’s not accessible to other people using Facebook. https://www.facebook.com/help/224562897555674
It’s also important to know that copies of your information may remain after the 90 days in backup storage that Facebook uses to recover in the event of a disaster, software error, or other data loss event. Facebook may also keep your information for things like legal issues, term violations, or harm prevention efforts. You can read more about this in the Data Privacy section of Facebook.
Can I cancel my account deletion?
If it’s been less than 30 days since you initiated the deletion, you can cancel your account deletion. After 30 days, your account will be permanently deleted, and you won’t be able to retrieve your information. If you sign in within 30 days and cancel the request, your account will be restored and it’ll be like you never left.