Not sure if this is the right place for it, but here it goes:
When I first used kde the most cool thing I found is that kde adapts with the user actions. I'm not a expert so I don't know how to tell exactlly what I mean with adapt, but let me try. Things like when you open kate, or any other window for instance, and it opens not maximazed and then you maximaze it and close. When the same program is opponned again it must open maximazed, this is not happening now. Other example is when you search for something in places or in apps, the most used aplication or file becomes the more upper option in the list. This is not happening anymore.

It is like kde have become idiot for now. I think you get the point, kde is not adapting with the user making chooses and making it easier after, it's not "learning" anymore.

I'm using kubuntu 15.10 and with another user this thing works great, but not with mine. I think there's some sort of configuration that I must have disabled or anything. I don't want to lose all my configuration, just want kde learning again.

Yup, mine did the same thing on Fedora when it upgraded from 5.4 to 5.5.

I didn't end up finding what caused it, just ended up renaming my profile (as root) to me.old, then doing a Can't remember for certain but I think I got the -R & -r correct. Always have to look up the man page for commands to see which -r or -R I need to use, but I THINK I'm correct there.

Anyway, this will create a "base" profile again, then log in and all KDE stuff would be recreated. You can then copy over firefox, chrome, thunderbird, etc. profiles/settings to your new profile so you don't have to set EVERYTHING up again.

This obviously would be a last resort, if you end up with noone knowing which files need to be modified to reset KDE to function correctly.

I suggest a message at https://bugs.kde.org/