Content Pane on Landing Page not getting Context
Ok, the solution is pretty easy, but due to Views complexity it took my some time to figure it out. In my setup, there is no filter available. My mistake was, that I thought there IS a fitler available which is why I did not fill in the upper section. Since my filter is not in the url, I had to select "Load default filter from node page, that's good for related taxonomy terms".

That's all the magic ;)