Apps icons do not appear in Windows 10 start menu

Hello, if you don't have
- system restore points
- a system image (created by Windows utility)
- disk images (highly recommended to allow recovery from tricky situations without technical help)

then you can try an in-place upgrade repair install.

(You could try
sfc /scannow
from an elevated command prompt, but somehow I'm not convinced that will fix this, although I've no evidence).

An In-place upgrade repair install will fix many things, but not those where the settings are not changed by the procedure.

For this you need an installation medium with the same base build as you have installed.
Repair Install Windows 10 with an In-place Upgrade - Windows 10 Forums
This will refresh Windows, after the manner of a Windows installation.
- all/most associations will be unchanged
- all your programs will be left installed
- you will lose any custom fonts
- you will lose any customised system icons
- you may need to re-establish your Wi-Fi connection
- you will need to redo Windows updates subsequent to the build you have used for the repair install
- Windows.old will be created
- system restore will be turned off- you should turn it on again and I recommend you manually schedule a daily restore point.
- you will need to redo any language downloads including the display language if you changed that)

This is one of the better features of Win10: as each major build comes out, that's your updated reference build, and as updates are mostly cumulative, there will be few to do.

Recommendation:
Before you perform this major repair procedure, do create a disk image.

Please consider using disk imaging regularly. It's a brilliant way to
- preserve your system (and your sanity)
- back up your data
- restore your system to a previously working state in a relatively short time

Recommended: Macrium Reflect or Aomei Backupper (free) + their boot disk/device + large enough external storage medium.