Critical Error on start-up

Hi
I have a ; Critical Error : Start menu and Cortana aren’t working. We’ll try to fix it the nex time you sign in, window pop every times i start my pc and this window stay there unless i click on sign out now… i’ve google it and people say they fix this problem by uninstalling Avast. Any other solution ? Thx

Please (re)search before posting.
There are already posts with solutions that has worked for people on this webboard and in other places.

http://lmgtfy.com/?q=cortana+not+working+windows+10
http://lmgtfy.com/?q=cortana+avast+site%3Aforum.avast.com

Reboot your system into Safe Mode with Networking.
Next, reboot your system into regular mode.
That should fix your problem.
Updating to the latest version of Windows 10 will also take care of the problem.