Dynamically inserted View is pushing other View out of Screen [Android]

Hi everyone,

I have a MasterDetailPage where the Detail looks like this:

SearchBar (not visible at the beginning)
Header
WebView
Advertisement

Everything inside of a StackLayout.

As said above the SearchBar is not visible at the initial showing of the Page but when a Button in the ActionBar is pressed that showns the SearchBar (and the whole layout gets shifted to the bottom) the Advertisement gets pushed out of the phones screen. I tried a ForceLayout already but with no success.

Any tips or hints on this?