Problem with iOS

I use Xamarin Forms to create an App, It works well on Android and Wp,but on iOS,there are several problems.

1. I have two ToolbarItems in the Navigation Bar, but the image is too huge when displayed in iOS

2. Some pages work well Android and Wp,but can not be fully rendered on iOS, an it will not display scroll bar, even I use a scrollview to wrap the content.

3. Images are so huge when it display on iOS