Ok, found some time to investigate. First I saw the BMW addon only in the marketplace content manager when searching for LIPB. And that’s what I saw
In DevMode I found the scenery package order tool with some rankings and corrected them for bmw scenery (3) and microsoft scenery of the airport (2). With some success.
Then I realized that I could click/open the World Update with the list icon on top and single-selected the Microsoft LIPB airport - and deleted it.
The result looks way better
I don’t know whether that’s the correct way to solve this but it seems to be working 
So thanks for the advice @BMW969