Others here may give you better ideas, but if you install that German Language Office 2010 and it actually installs as German without any choices to change the language during the install process, then you may be able to change the language with Microsoft's Office 2010 Language Pack.
But that web site may tell you more. Search around that site as I also found this page there; Determine if you need a language pack or language interface pack.
Good luck, and I hope that helps.
Mark

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