Xaml not behaving correctly in position - xamarin.forms

Question

For some reason my button is not showing I want the bottom to be at the bottom and green but its not. Also is their any kind of editor for grids and placements of controls would make this easier.
<ContentPage xmlns="http://xamarin.com/schemas/2014/forms" xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml" x:Class="WellbeingNinja.Views.RunningPage">
<ContentPage.Content>
<Grid Padding="30,40,40,10">
<Grid.RowDefinitions>
<RowDefinition Height="200" />
<RowDefinition Height="200" />
<RowDefinition Height="200" />
<RowDefinition Height="200" />
<RowDefinition Height="200" />
<RowDefinition Height="200" />
<RowDefinition Height="200" />
<RowDefinition Height="200" />
</Grid.RowDefinitions>
<Grid.ColumnDefinitions>
<ColumnDefinition Width="50*" />
<ColumnDefinition Width="50*" />
<ColumnDefinition Width="*" />
<ColumnDefinition Width="*" />
</Grid.ColumnDefinitions>
<StackLayout VerticalOptions="Center" HorizontalOptions="Center">
<Label x:Name="lblduration" Text="Duration"></Label>
</StackLayout>
<Frame Grid.Column="0" Grid.Row="0" x:Name="frameTotalSpeed" VerticalOptions="StartAndExpand" CornerRadius="2" >
<StackLayout>
<Label x:Name="lblSpeedText" Text="Speed(miles)"></Label>
<Label x:Name="lblSpeed" VerticalTextAlignment="Center" HorizontalTextAlignment="Center" Text="0.00" FontSize="Large" ></Label>
</StackLayout>
</Frame>
<Frame Grid.Column="1" x:Name="frameTotaldistance" VerticalOptions="StartAndExpand" CornerRadius="2" >
<StackLayout>
<Label x:Name="lblDistance" VerticalTextAlignment="Center" HorizontalTextAlignment="Center" Text="0.00" FontSize="Large" ></Label>
<Label x:Name="lbldistanceText" Text="Dist" HorizontalOptions="Center"></Label>
</StackLayout>
</Frame>
<Frame Grid.Column="0" x:Name="frmTotalMilesLeft" Grid.Row="1" VerticalOptions="StartAndExpand">
<StackLayout>
<Label x:Name="lblDistanceLeft" VerticalTextAlignment="Center" HorizontalTextAlignment="Center" Text="0.00" FontSize="Large" ></Label>
<Label x:Name="lblavgPace" Text="Avg Pace (Min/Mil)"></Label>
</StackLayout>
</Frame>
<Frame Grid.Column="1" Grid.Row="1" x:Name="frmTotalCarolesBurned" VerticalOptions="StartAndExpand">
<StackLayout>
<Label x:Name="lblTotalCalories" VerticalTextAlignment="Center" HorizontalTextAlignment="Center" Text="0.00" FontSize="Large" ></Label>
<Label x:Name="lblTotalCaloriesBurned" HorizontalOptions="Center" Text="Calories Burned"></Label>
</StackLayout>
</Frame>
<Button Grid.ColumnSpan="2" Grid.Row="3" Text="Start Workout"></Button>
</Grid>
</ContentPage.Content>

Answer 1

If you give each row with a fix height 200, then the Y position of row 3 is start from 600 and it may larger than the height of the screen. You add the Button at row 3 and it is out of the bounds of the screen. Then you won't see it in the screen.
Use a Auto would be better, it will automatically sizes to fit content in the row or column. You can also set the ColumnSpacing and RowSpacing to add some space between row and columnspace:
<Grid Padding="30,40,40,10" ColumnSpacing="30" RowSpacing="70">
<Grid.RowDefinitions>
<RowDefinition Height="Auto" />
<RowDefinition Height="Auto" />
<RowDefinition Height="Auto" />
<RowDefinition Height="Auto" />
<RowDefinition Height="Auto" />
<RowDefinition Height="Auto" />
<RowDefinition Height="Auto" />
<RowDefinition Height="Auto" />
</Grid.RowDefinitions>
<Grid.ColumnDefinitions>
<ColumnDefinition Width="60*" />
<ColumnDefinition Width="60*" />
<ColumnDefinition Width="*" />
<ColumnDefinition Width="*" />
</Grid.ColumnDefinitions>
Read the document about Grid to get more information and you can use StackLayout to achieve the UI too.