Starting with Windows 8 Microsoft has a replacement/alternative “start menu” that is accessible via the Windows+X key.
If the Windows+X, or right-click Start, does not work then check path to these files/folders/apps menu items at: %LOCALAPPDATA%\Microsoft\Windows\WinX
If that folder does not exist try copying it from another user’s home/profile path.
To restore the “Start” button and menu options you can try this one liner from an “Administrator Command Prompt”:
dism.exe /online /Cleanup-Image /StartComponentCleanup & dism /online /cleanup-image /restorehealth & sfc /scannow & pause