Sorry to hear you are having trouble.
Could I get you to go to:
C:\Program Files (x86)\Stardock\Groupy\lang
Rename zh-cn.lng to zh-cn.OLD
Unzip this file there, re-open the Groupy UI and see if it's correct?
If it is incomplete (which I surmise it is), would you be willing to work with us on some translations? I could make it worth your while by adding products to your account.
Sorry for the issue and thanks for the time.
Stardock Support Manager