High Sierra- Partition error
Have you tried all startup commands to try to get to the recovery screen? One of these should get you out of the black screen.

Command+R

Command+Option+R

Command+Shift+Option+R

Or

Just the option Key

Hopefully you will get into recovery mode to use terminal.
- Open Terminal and type the following command (without quotes) “diskutil list”

-Terminal should give you a breakdown of the disks and volumes that are currently on your Mac that you may not see in disk utility.

Anyway you can post the picture of diskutil list?

Also what Mac version do you have?