New
#1
Suggestions :
1. Right click at Start button > click Command Prompt (Admin) > type powershell > press Enter.
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.
2. Create another user account with exactly the same account type > logon to it and see if you have the same problem or not.
P.S. This is not a solution, but give this a try...........
Right click at an open spot of the desktop > select Personalize > left side, click Start > right side, scroll to "Use Start full screen" and turn it to ON. Does Start Menu open up ?
Sorry. I don't know how to fix the "slowness" issue.