forgot admin password for my mac

You might give this a try:

How to Create a New User Account if You Cannot Access Your Admin Account

Reboot the computer. At the chime press and hold down the COMMAND-S keys to start into Single-user Mode. You will boot to a black screen with scrolling white text, release the keys and wait until it finishes. Enter the following lines at the command prompt pressing RETURN after each:

    mount -uw /

               ^     ^  Note spaces

    rm /var/db/.applesetupdone

        ^    Note space

    reboot

After you reboot the computer you will be taken to the Setup Assistant. When you get to the point where you are asked to set up your new user account, create a new admin account. Be sure to name this user account something different than the admin user account that already exists on the system. When you finish the Setup Assistant, it will automatically log you into the new account.

You can transfer your files from the old account to the new one. See Transferring files from one User Account to another. Once you have moved all your files into your new account, you can delete the old account using Accounts or Users & Groups preferences.

Change or reset the password of a macOS user account - Apple Support

You can create a new administrator account by restarting the Setup Assistant:

1. Boot into Single User Mode: Start/restart your Mac. As soon as you hear the startup tone, press and hold ⌘ + S until you see a black screen with white lettering. (If you end up back on the login screen after a flash of the black screen with white lettering, enter your password and it will return to the black screen.)
2. Check and repair the drive by typing /sbin/fsck -fy then ↩ enter - as directed by the on-screen text.
3. Mount the drive as read-write by typing /sbin/mount -uw / then ↩ enter.
4. Remove the Apple Setup Done file by typing rm /var/db/.AppleSetupDone then ↩ enter.
5. Reboot by typing reboot then ↩ enter.
6. Complete the setup process, creating a new admin account.

Be very careful to notice the spaces in those Terminal Commands.

Once you've done that the computer reboots and it's like the first time you used the machine. Your old accounts are all safe. From there you just change all other account passwords in the account preferences!!