I would improve the look a little more and try to find ways to get more visitors to the site.

Perhaps making the social buttons a little bit more prominent?

I was going to suggest using Google tag manager if you were using Google analytics to get an idea of how well visitors are performing certain goals, but I see you are using piwik. I am not sure if piwik has these same types of features.

I do not speak German, but I did like I could switch to English. However, I noticed the hover menus still display in German.