i imagine the same rules would apply. Good quality content pertaining to and optimized for desired keyword phrases. Promote the site/offering within your niche. Focus on driving relevant traffic and qualified users. Grow user/customer base naturally and steadily by watching (analytics) and listening (customer care).
You have to build links in German directories and sites then after you will get good position.
You have to get backlinks in normal ways as you are doing apart from that you have to get backlinks from .de sites too. That will help to get good rank on Google in Germany.
Preferably, the text is in German but most importantly, you should get more links from Germany as it would have more weightage.
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