your dataview of Maschinen has the 2 attributes. In mendix you should use Reference selector instead of dropdown if you want to change the attribute in the same dataview. If you select an other Kostenstelle, the dataview Maschinen will only have those objects that have that kostenstelle if you use a reference selector.
In a reference selector you can set the selectable objects. You can use a microflow or xpath to only show those Kostenstelle belonging to the Machine selected (I usually use microflows, since it's easier to use than xpaths).
Is that an answer to your question?