Run Command Prompt or PowerShell  as administrator and enter the following commands to repair Windows system files. Once complete reboot and try running the update again.

DISM /Online /Cleanup-image /RestoreHealth

SFC /Scannow

DISM (Deployment Image Servicing and Management) manages both Windows Online and Offline Images and repairs system files

• /Online switch instructs DISM to target the running Operating System instead of an offline Windows image (.wim) file or virtual hard disk (.vhd or .vhdx)
• /Cleanup-Image switch performs cleanup and recovery operations on the running Operating System
• /Restorehealth switch scans the running Operating System for corrupt files and attempts to fix them

SFC (System File Checker)

• /Scannow will scan all protected system files, and replace corrupted files with a cached copy that is located in a compressed folder at %WinDir%\System32\dllcache