Only one template was translated. Other templates - p. ex the template for posts (hidden link) were NOT translated (see heading in the sidebar which is still in German; weird as well: The related posts being shown in the sidebar are different German/English, even with all posts being translated).
Update:
The following is weird because I am sure it worked when I checked on Friday night. But now the sidebar is again not fully translated. Just compare yourself: hidden link hidden link
I have no clue why it worked and now no longer works. But I leave this for later.
Let me rephrase the issue:
On pages that use custom templates (single posts and portfolio items), only the German template loads; the English version reuses the German sidebar (heading still in German).