kde gets slow and returns fast with relogging

somehow my KDE opensuse occasionally gets a little slow after a long while of usage , however it’s more than enough to log out and in again to KDE and its fast again at once , what is this ???

Could it be that your RAM gets eaten up and the system starts to swap?
Run “free -h” in a terminal window (konsole f.e.) to check, or use KDE’s Systemmonitor.

Or maybe some processes run that use your CPU? Press Ctrl+ESC to see them.
There is a problem with some screensavers f.e. that they keep on running in the background when you unblank the screen.
So this could slow down your system when it is running for a long time.