The only solution for me was to remove my user account and add it again.
Now everything is working as expected (included the non-working search).
Apps are working as normal again.

My profile...

Thanks,

No, I used to have Start8 installed when I still had Win 8.1 but that's no longer the case as I like the new start menu better.

I'm also facing with a lot of problems under my...

Any idea what to do when all options in "choose which folders appear in start" are greyed out?

It woks just fine for another account on the same computer but for me (the main and 1st admin...