I envy all of you multiple language folks! Forty years ago I spoke French as well as English, but the French went by the wayside as the years passed by.
I don't know if this will help you, but open the KDE Control Center. Then open the
Regional & Accessibility option. Select the
Enable keyboard layouts option and explore if those options help you. You might want to look at the
Kxkb options in the same section. Also take a look at the KDE docs in the KDE Help Center or here online:
Configuring KDE.