Hey suefromrandolph,
There's not a way to know how long it will take, as this is completely dependent on the amount of data being deleted.
For more info on deleting a user account though, check out these steps:
Delete a user or group on Mac
If you’re an administrator, you can delete users that you no longer want to have access to your Mac. You can also delete groups you don’t want.
1. On your Mac, choose Apple menu
> System Settings, then click Users & Groups
in the sidebar. (You may need to scroll down.)
2. Click the Info button
next to the user or group you want to delete, then click Delete Account.
Note: If a user is logged in to this Mac now, you can’t select them.
3. Do one of the following:
• Save the home folder as a disk image: Select “Save the home folder in a disk image.” This archives all the user’s documents and information so the user can be restored later if needed. The disk image is saved in /Users/Deleted Users/.
• Leave the user’s home folder as is: Select “Don’t change the home folder.” The user’s documents and information remain and the user can be restored later if needed. The home folder remains in /Users/.
• Remove the user’s home folder from the computer: Select “Delete the home folder.” The user information is deleted and the storage space is freed.
• Delete a sharing-only user or a group: Click OK.
A sharing-only user doesn’t have a home folder.
4. Click Delete Account.
This is outlined in more detail here: Delete a user or group on Mac
If the process doesn't complete as expected though, don't hesitate to reach out to Apple Support using this link: Get Support
We hope this helps out.
Take care!