Removing deleted backup folders from Trash

[LizEng]

I have a MBP 2015 256GB, running Mojave and I am seriously running out of space. My System folder has 139GB of space which cannot be accounted for. I've pinned it down to old deleted (invisible) Time Machine backup folders that are still on my external HDD.

I've tried this method -

- to access and delete these folders, but I keep getting these errors about Authentication Plugins.

I am in no way experienced or knowledgeable enough to pretend to know what I'm doing, but common sense tells me that I should be able to delete them as I don't need them (Yahoo? Really). Google searches tell me that they are WordPress related, but I don't use WordPress at the moment, and I've started using Adobe Muse after April. I thought that it could be Muse, but this oldest backup folder is from 29 March, where the plugins are already an issue.

Is there ANYONE who has had anything remotely similar to this and can point me in the right direction?

P.S. I use most of the Adobe Creative Cloud programs as I'm a Digital Marketer/Graphic Designer and I know that these programs are very resource intensive

 

[ponder]

Close all the applications using the Volume, unmount it, mount it back and run:

diskutil verifyvolume /Volumes/"Backup Drive"
diskutil repairvolume /Volumes/"Backup Drive"

Now try deleting again.

If that does not work boot from a linux liveusb stick and try deleting from there via file manager or console (command syntax is the same)

 

[Pineapple Smurf]

i use OmniDiskSweeper to view my files and sift through them and delete kak
Works well
free app