Then let it try again. If it fails, look at a test with SAFE MODE (google if you need to know how.)

If Safe Mode fails it's time to consider if the backups are current. I use two methods when the owner is not sure. 1. I pull the drive into some USB case so they can copy their files out. 2. I boot up a current Linux to copy the files out. No learning Linux. We are only using the file manager and it works like Windows except no drive letters.

After the files are safe we try booting our W10 Install and repair USB Stick or DVD. If you don't have that google how to make one with "Microsoft Media Creation Kit." Boot that and try automatic repairs. If that fails, try the safer "Keep my files" option of the Windoes resets (read https://support.microsoft.com/en-us/help/12415/windows-10-recovery-options )