Need help to create StackLayout menu

How can I create menu for this template?

That's how I tried:)

Button btn1= new Button()
        {
            Text="Button 1",
            HorizontalOptions = LayoutOptions.FillAndExpand,
        };       
        Button btn2= new Button()
        {
            Text="Button 2",
            HorizontalOptions = LayoutOptions.FillAndExpand,
        };
        Button btn3= new Button()
        {
            Text="B3",
            WidthRequest=40,
            HeightRequest=40
        };
        StackLayout menuLayout = new StackLayout()
        {
            Orientation = StackOrientation.Horizontal,
            HorizontalOptions = LayoutOptions.StartAndExpand,
            Children = { btn1, btn2, btn3 }
        };