APFS formatted disk with too much purgeable and hidden system space that can't be deleted

I have the problem that trashing large files doesn't free up extra

space. I had 88 GB free and trashed more than 70 GB of unnecessary

files. I emptied the trash, but the space available was now only 80 GB!

I ran daisy disk and deleted the 142 GB of purgeable space but only 5 GB

was recovered. I cloned the Macintosh SSD APFS to a hard drive APFS.

Get info gives me:

SSD: Capacity 500 GB Available 85 GB Used 414 GB (purgeable not mentioned!!!!)

HD: Capacity 502 GB Available 224 GB Used 468 GB (190 GB purgeable)

Daisy disk gives me now:

hidden space 296 GB

purgeable space 137 GB

still hidden 159 GB

I am running Mojave 10.14.5 on a Mac Pro 2010 with Accelsior S and a Samsung EVO 850 mounted on this pci-e card.

In terminal: tmutil listlocalsnapshots /

com.bombich.ccc.69E7809D-C206-4AE7-9639-C5D7BD002542.2019-05-30-205103

com.bombich.ccc.1563A712-C094-4FCD-9155-82F8BEF440B0.2019-06-24-175603

com.bombich.ccc.41BFC9B1-36D7-45C6-BAE7-0B4C5A8F04AB.2019-07-05-095015

com.bombich.ccc.B13EE9D1-381D-4ADA-B988-73B7B2B193D4.2019-07-16-221928

If I could go back to HFS+ I would do that immediately, but then I can't update Mojave anymore.

So I have to stick with that pesky APFS.

What can I do? Please help. TIA