start menu is not working and cortana

suddenly my start menu and cortana is not working
please help fast

How long ago is "suddenly" ?
If it is not too long ago, please do a system restore. Pick a date when you did NOT have this problem as your restore point.
System Restore Windows 10

If system restore does not solve the problem, try this...................

Right click at it > click Command Prompt (Admin) > type powershell > press Enter key.
At the flashing prompt, copy and paste this command line ( to avoid typo it's best to apply Copy/paste method)......

Get-AppXPackage -AllUsers | Foreach {Add-AppxPackage -DisableDevelopmentMode -Register "$($_.InstallLocation)\AppXManifest.xml"}

> press Enter.

When it is done, check if you can open Start Menu.