Hi
To get into Windows I had to user Boot Step by step advanced startup option.
I got to this by hitting the reset 3 times in succession, as it was trying to start Windows, then selected advanced Startup.
Once in Windows it worked OK, but if it restarted... Black Screen!
I wasnt able to fix the problem on my own.
I called Microsoft support, and they got a senior technician to call me back.
He was very knowledgeable, and in an hour he had cleaned up Windows, removing all Antivirus and startup programs, and non Windows services. He was too quick for me to see exactly what else he had done.
But once he had this sorted, I reinstalled Windows 10 Pro (from their site)
Then I did the update to version 1803.
It has been working like a dream since then.
This guy was an absolutely master technician I was watching him work remotely on my PC, and he knew his oats... I cannot praise him enough.
He said the possible reasons for the windows update failing - is
Anti-Virus,other Security programs, and startup programs and services, which may block the process and cause corruption...
Good Luck