How to change the interface language of the system please?

Hi there,
Im kinda new to the KDE, only tried it 10 years ago (on suse 8.0), but actually have been using Ubuntu and Fedora (Super OS and Russian Fedora Remix actually) for last few years. And since im not quite sure yet wether i like the Gnome thing anymore or not. And Super OS is discontinued and Russian Fedora Remix is kinda to dynamic to my liking. And i kind of dont really like Mint because it smells Gnomeish maybe or something to my liking. Tried OpenSuse on my HP Work laptop instead of RFRemix and liked it alot. And after looking around some more found Netrunner. Also like it alot as a replacement for Super OS.
Well i went to the language and regional settings somewhere in the configuration settings and changed the language to Russian. And it seems to me that the changes qre applied not everywhere.
Is there anything i can do about it?
Thanks in advance,
Nikolai