AdMob Layout Issue

Hey there!
The Ad works fine, but the Behaivior in the ScrollView is not like Expected. So therefore I set:
<NativeViewHost RenderToTexture="true" > And now it behaves great.
But the Problem is, that if I go to the Page where the ad is (I have to scroll a bit down), then the Ad loads at the top of the Page (not expected) and also in the NativeViewHost. But the first visible Ad should not be there and is above another elements.

Edit: If i set <NativeViewHost RenderToTexture="false" > the Problem is, that the Ad is (when I scroll) always on Top. I have a Top Menu for the Subpages and when I Scroll the Ad is above that…

Does anyone know why?
(I hope you understand my Problem x) )