Xamarin Forms TabbedPage question

Hello everybody,

I was tinkering around with the TabbedPage (regarding to https://docs.microsoft.com/en-us/xamarin/xamarin-forms/platform/android/tabbedpage-toolbar-placement-color) but I have several problems.

On the xaml View I do not have the option to set
android:TabbedPage.ToolbarPlacement="Bottom"
android:TabbedPage.BarItemColor="Black"
android:TabbedPage.BarSelectedItemColor="Red"
while I can set them in the Code behind

My Visual Studio tells me that this Property can not be found. Instead I have only the choose between
android:TabbedPage.IsSmoothScrollEnabled
android:TabbedPage.IsSwipePagingEnabled
android:TabbedPage.OffscreenPageLimit

Also when I debug with the Android emulated device the

are not shown side by side, only one of them and the other two are invisible.

I am using Xamarin.Forms 3.6.0.264807 within a .net standard project.

What am I doing wrong or what am I missing?

Yours