this is best solution.
<Setter Property = "HorizontalOffset" Value="50"/>
<Setter Property = "VerticalOffset" Value="50"/>
<Setter Property = "Background" Value="#6BC16C"/>
<Setter Property = "Foreground" Value="{DynamicResource MainBlueColor}"/>
<Setter Property = "FontSize" Value="14"/>
<Setter Property = "FontWeight" Value="Bold"/>
<Setter Property = "FontFamily" Value="Roboto"/>
<TextBox x:Name="tbKeymsgGoal" TextAlignment="Center" Margin="0,60,0,0" Style="{StaticResource SpeechProWaterMarkStyle}" Tag="e.g.Resources" FontFamily="Roboto" FontSize="14" FontWeight="Normal" TextWrapping="Wrap" HorizontalAlignment="Center" Width="200" Height="30" Background="{DynamicResource SlideContent.White}" Template="{DynamicResource TextBoxBaseControlTemplate}" VerticalAlignment="Top" Padding="5" Foreground="{DynamicResource MainBlueColor}" >
<TextBox.ToolTip>
<ToolTip DataContext="{Binding Path=PlacementTarget,RelativeSource={x:Static RelativeSource.Self}}" Style="{StaticResource MyTooltip}">
<TextBlock Text="{Binding Text}" TextWrapping="Wrap" Width="200"></TextBlock>
</ToolTip>
</TextBox.ToolTip>
</TextBox>