Hello,
For a few days I am encountering a issue with my desktop.
Every time I start my PC there is this ugly wallpaper and no widgets or icons are showing.
Also I am turning off PC by the terminal because power buttons from application launcher are gone.
My apologies. I misremembered. The files are in the ~/.config directory, and are:
plasma_calendar_astronomicalevents (calendar settings for various widgets)
plasma_calendar_holiday_regions (calendar settings for various widgets)
plasma-dataengine-extsysmon.conf (Widget access to system info settings)
plasma.emojierrc (I dunno.)
plasma-localerc (Language/numerics settings)
plasma-nm (Network Manager settings)
plasmanotifyrc (Notifications setting)
plasma-org.kde.plasma.desktop-appletsrc Every other setting - desktop settings (including wallpaper and wallpaper engine) widget placement, size, specific options, etc) This is the really important one.
Infrequently, plasma-org.kde.plasma.desktop-appletsrc can be corrupted. If you have read/write to it, and it's there, then restore from backup is your best tack.
Well, with 2. I actually meant to see if it was working and then use the new user, transfering the relevant files.
I understand you'd have to reconfigure a lot of things, but at least you have a backup solution...
This can become your opportunity to learn more about how linux and kde work.
If you donโt have time for that, just use the new user.
Do not forget, when using sudo/root power to administer your system, you need to be responsible, having read relevant manuals, wikis etc., or it is not unexpected to break your system.
As @petsam has intimated if you have messed something by using root when you shouldn't, you could try resetting all permissions to the default in your home user directory.