Huge bug on windows 10

Since yesterday, when I launch my pc, start menu and cortana won't work, and all my desktop shortcuts disappeared apart from the bin and one game which is weird. Moreover, last updates are impossible, and all options given by Windows always fail. Also, even if I create new icons they disappear when I reboot the pc. Lastly, my wallpaper also changed to the default one.
If anyone could help, it would be much appreciated.