First I installed WP, then I installed BP and activated BP’s default theme. I didn’t change anything in the PHPs.
When I go to the design section (or “Apperance”? -> I’m using a translated (German) version of WP and BP so I’m not entirely sure how the sections are called in the English version, sorry) in the dashboard and the choose “Editor” the files of “BuddyPress Default” are already shown as to see on the top right. When I choose the index.php then it shows me the code I posted before!
How can that happen if the code should be totally different???