How to costumize ComboBox in WPF (items list)?

So far I was able to customize my ComboBox to appear in rounded corners by editing the style but the list Items doesn't appear if I click on it:

<Style x:Key="RoundedCombeBox" TargetType="ComboBox">
    <Setter Property="Template">
        <Setter.Value>
            <ControlTemplate>
                <Grid Background="Transparent">
                    <Rectangle StrokeThickness="1" Stroke="Black" RadiusX="20" RadiusY="20" Fill="#FFFFFF" IsHitTestVisible="False"/>
                    <TextBox Background="Transparent" BorderThickness="0" TextAlignment="Left" FontSize="15" FontFamily="Inter_Font" FontWeight="Bold" Padding="20,10,20,0"/> 
                </Grid>
            </ControlTemplate>
        </Setter.Value>
    </Setter>
</Style>

I though that my problem maybe because of me using a TextBox. if that's the problem then what's the best way of doing it or how to make textbox suggest and append items?