Installation difficulty

Trying to install new WD 5 T external hard drive to a Macbook Pro, Sonoma 14.5 . I get as far as trh\ying to erase My Passport on the Disk Utility, but then it fails. The message box says: The Volume “My Passport” on disk4s1 couldn’t be unmounted because it is in use by process 34157 j(diskimagesiod). Couldn’t unmount disk.
HELP please!

Whom told you, that this forum serves OS support, HOW TO?
Stop trying and visit a Macbook specialist (locally), and pay the man.