MacBook Pro Dying After High Sierra Release

How do you have 99GBs free then no GBs free on the same drive with no changes? Do you know what you are looking at?

Get Correct Storage Information

Do not use the information from the Storage section of the About This Mac dialog. Ignore the Storage information as it is typically wrong. To find out the correct information for any disk: Select a Desktop disk icon. Press Command-I to open the Get Info window and look at the topmost panel displayed. You will find the disk information displayed for Capacity, Available, and Used. If you have more than one disk/partition then repeat for each one on your Desktop.

So, after doing the above how much space is Available? Why can't you use the computer? If you have bricked it and it won't boot up then you should do the following:

Install El Capitan or Later from Scratch

Backup if possible before continuing.

1. Restart the computer. Immediately after the chime hold down the CommandandRkeys until the Apple logo appears. When the Utility Menu appears:
2. Select Disk Utility from the Utility Menu and click on Continue button.
3. When Disk Utility loads select the volume (indented entry, usually Macintosh HD) from the Device list.
4. Click on the Erase icon in Disk Utility's main window. A panel will drop down.
5. Set the Format type to Mac OS Extended (Journaled.)
6. Click on the Apply button, then wait for the Done button to activate and click on it.
7. Quit Disk Utility and return to the Utility Menu.
8. Select Install OS X and click on the Continue button.

Disk Utility reports different information if the drive uses Core Storage. With Core Storage, you have a "container" which is the physical disk whose size is the capacity. In the container is a logical storage unit whose capacity is the amount of data currently stored. Hence, two different capacity reports. They only appear to be conflicting.

APFS, the new file management and formatting system is a bit like Core Storage in that there is a physical disk on which there is a container that includes the logical volume and three other, small volumes.

You really don't have to know all that stuff. Disk Utility knows it as does OS X. All you need know is how much storage space is available. That you can find using what I outlined in my earlier post - Get Correct Storage Information.