    <StackPanel  xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
         xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml">
        <TextBlock HorizontalAlignment="Center" Foreground="Red" FontSize="50" FontWeight="Bold">
        <TextBlock.Triggers>
            <EventTrigger RoutedEvent="TextBlock.Loaded">
                <BeginStoryboard>
                    <Storyboard>
                        <StringAnimationUsingKeyFrames
                            Storyboard.TargetProperty="Text"
                            Duration="0:0:5" RepeatBehavior="Forever">
                            <DiscreteStringKeyFrame Value="Wygrałeś" KeyTime="10%"/>
                            <DiscreteStringKeyFrame Value="" KeyTime="20%"/>
                            <DiscreteStringKeyFrame Value="100" KeyTime="30%"/>
                            <DiscreteStringKeyFrame Value="100 000" KeyTime="45%"/>
                            <DiscreteStringKeyFrame Value="100 000 zł!!!" KeyTime="60%"/>
                            <DiscreteStringKeyFrame Value="" KeyTime="70%"/>
                            <DiscreteStringKeyFrame Value="Wygrałeś 100 000 zł!!!" KeyTime="75%"/>
                            <DiscreteStringKeyFrame Value="" KeyTime="80%"/>
                            <DiscreteStringKeyFrame Value="Wygrałeś 100 000 zł!!!" KeyTime="85%"/>
                            <DiscreteStringKeyFrame Value="" KeyTime="90%"/>
                            <DiscreteStringKeyFrame Value="Wygrałeś 100 000 zł!!!" KeyTime="95%"/>
                        </StringAnimationUsingKeyFrames>
                    </Storyboard>
                </BeginStoryboard>
            </EventTrigger>
        </TextBlock.Triggers>
        </TextBlock>
    </StackPanel>