The NavigatorFree suggests as routing to turn from the "Bördestraße" to the "Oberbergheimer Straße" and then return to the "Bördestraße" (see screenshot, red route, https://share-your-photo.com/8050e5b721). This route is physically longer. On both streets is maxspeed=50 specified and there are no further restrictions (turnings restrictions or similar) which (from my point of view) would prefer this way.