OnInspectorGUI content overlaps Editor Window content

Hi!

I need to draw the default inspector of a selected object at the bottom of an editor window. So far so good, my last step in OnGui() is:
UnityEditor.Editor.CreateEditor(selectedObject).OnInspectorGUI();
this works perfectly fine, but:

If I draw the editor for materials (MaterialEditor) the damn thing overlaps over my existing UI. It just starts at 0,0 like as if it forgot the order of things.
I know about the extendable header MaterialEditor.DrawHeader() but adding it won’t solve the problem, it gets even worse and throws a bunch of red errors. Also I don’t really need it, its even more compact without it.
Do you guys know how I can order the OnInspectorGUI stuff?

Here is how it looks like:
6472124--726530--EvilInspector.png

Are you supposed to call “DrawDefaultInspector()” rather than “OnInspectorGUI()”?

forgot to mention that I tried that as-well. But if I do that, the formatting of the inspector gets lost :confused:
See here:
6473111--726734--Bildschirmfoto 2020-10-30 um 10.00.26.png