I found this by googling a bit:
Your keyboard will need a bit of remapping, or else the ":" or the "/" keys will not work. Click the KDE Control Center icon (big one at the bottom that looks like a colour monitor with a card in front of it) or get there via the Menu. There, go to Regional & Accessibility -> Keyboard Layout and change it to US English (from the default of German).
Note: The changes you make here are only for the said user, and do not apply globally. If you create another user, the above steps of "localisation" will need to be repeated.
Or, you could re-install and take more care in selecting the language, regional, keyboard, and other otpions to make such options global for all users.