Don’t worry apply solutions listed here to fix the problem.
Also with Windows 10, Microsoft made it mandatory to download and drop in the latest windows updates Automatically.
But what happens is that the update or windows installation says it failed.
double-check you have a stable working internet connection to download windows updates from the Microsoft server.
Also, you might download and initiate the officialWindows Update Diagnostic too as well.
After complete, the process Restart windows and again manually Check for Updates.
Reset Windows update component
Still, need help, windows update stuck downloading or fails to install?