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If the company in Germany refuses to take the game back, check your consumer rights first.
You may be entitled to return the game for a refund under the EU's Directive on Consumer Rights:http://ec.europa.eu/justice/consumer-marketing/rights-contracts/directive/index_en.htm
You can quote this directive to the company before proceeding with any official action against them - it may make them think twice.
Another alternative course of action you may take is to sell the game on eBay and buy an English version of the game for a similar amount.