I also live in Germany and have some of the ads in German. I suppose it's the result of behavioral targeting (the kind of targeting that uses information collected on an individual's web-browsing behavior, such as the pages they have visited or the searches they have made, to select which advertisements to display to that individual). This kind of targeting can be combined with contextual targeting (based on the surrounding content), or based on other factors like geography and demographics. For example, I see a lot of heine.de ads on my HubPages because I'm a buyer there and visit their site regularly. This means that people in other parts of the world don't have to necessarily see the same ads you do (and they probably won't).
These ads are part of the Google interest-based advertising program (behavioral targeting ad program) and there's a way to opt-out by clicking the "Opt out" button on the homepage of the Ads Preferences Manager. You'll have to delete your browser's cookies regularly though (unless you download the Google advertising cookie opt-out plugin).