I boot my Mac Pro 2009 from a Samsung SSD EVO 850 installed in an OWC SATA III pci-card. I checked the SSD with disk utility and the computer locked completely up. Upon restarting, the screen remained black.I booted in the recovery mode and was unable to repair the disk (unable to unmount). I replied the disk booting from another hard disk with Mojave. Then I selected the recovery mode again and tried to reinstall MacOS. A message appears (unable to connect to the internet). Why doesn't the recovery mode work? In one month APFS I had more problems than ten years HFS+.