go to this page:
choose the link to the packages for your distro and choose a mirror, download all the rpm inside.
Press "CTRL-ALT-F1", log as root and write "init 3" so you will be out of your X environment.
Now write "yast2" and go to uninstall all the rpm packages with the same name of the packages you downloaded before, logically the name will not be exactly the same because the version number on the downloaded rpm makes it a little different, but is easy to recognize.
Install all the rpm downloaded with the command:
rpm -ivh filename.rpm
start installing the QT and the libraries and after install the KDE packages.
When you'll end all this just write in console "init 5" and enjoy with the updated KDE
Make a backup before to do all this.