Please try these options one by one and check after each option.
- Run Start menu troubleshooter
- Reinstall Start Menu / Cortana
Windows Key+X > Click Powershell (Admin) > Copy the below and paste into Powershell > Enter > Reboot your computer
Get-AppXPackage -Name Microsoft.Windows.ShellExperienceHost | Foreach {Add-AppxPackage -DisableDevelopmentMode -Register "$($_.InstallLocation)\AppXManifest.xml"}
Copy and paste following into Powershell and Enter
Get-AppXPackage -Name Microsoft.Windows.Cortana | Foreach {Add-AppxPackage -DisableDevelopmentMode -Register "$($_.InstallLocation)\AppXManifest.xml"}
- Re-register All apps
Right click on Windows Start > Right click on Windows Powershell (Admin) > Copy the following from below and right click in Powrshell to paste ? Enter > Restart your computer
Get-AppXPackage -AllUsers | Foreach {Add-AppxPackage -DisableDevelopmentMode -Register "$($_.InstallLocation)\AppXManifest.xml"}
For MS Office problem - Try repairing your Office installation. First try Quick Repair (takes 5 - 10 mins) , if that doesn't help then try Online Repair (Takes more than 30 mins but less than 1 hour in general)
How to repair instructions -