right click start
choose Terminal (admin)
if it doesn't open as Powershell, click drop down arrow and select from list
copy/paste this command into window:
Repair-WindowsImage -Online -RestoreHealth
and press enter
Then type SFC /scannow
and press enter
Restart PC if SFC fixes any files as some fixes require a restart to be implemented
First command repairs the files SFC uses to clean files, and SFC fixes system files