I have a 500 GB external USB disk that contains a 465GB "APFS container", with Mac OS X Catalina, bootable (with the trick "Press and hold the Option (Alt) key immediately after turning on or restarting your Mac")
I need to use this disk for something else, and I need to move it to another 320 GB disk.
How to do that?
First how to shrink the 465 GB to 300 GB (only < 100 GB are used)? Is it possible from another Mac OS High Sierra computer or another Linux or another Windows computer?
Then how to copy the partition to the 320GB so that it will still be bootable?