First you should try downloading the installation file(s) and see if it does install German. If not then you have no problem. If it does then you might need to work with Customer Support (or whomever sold it to you) to get a serial number and download for an English version.
Chat support - For the link below click the Still Need Help? option in the blue area at the bottom and choose the chat option...
Make sure you are logged in to the Adobe site, have cookies enabled, clear your cookie cache. If it fails to connect try using a different browser.
Get chat help with orders, refunds, and exchanges (non-CC)
http://helpx.adobe.com/x-productkb/global/service-b.html ( http://adobe.ly/1d3k3a5 )