Win key on keyboard - type cmd - run as admin:
dism.exe /online /cleanup-image /restorehealth
wait for "the operation completed succesfully"
sfc /scannow
if everything was ok, you see the next message:
Windows Resource Protection found corrupt files and successfully repaired them.
For online repairs, details are included in the CBS log file located at
windir\Logs\CBS\CBS.log. For example C:\Windows\Logs\CBS\CBS.log. For offline
repairs, details are included in the log file provided by the /OFFLOGFILE flag.