MainWindow.xaml.cs

private ObservableCollection<User> users = new ObservableCollection<User>();

        private ListCollectionView View
        {
            get
            {
                return (ListCollectionView)CollectionViewSource.GetDefaultView(users);
            }
        }

private void filterBtn_Click(object sender, RoutedEventArgs e)
        {
            if(decimal.TryParse(paymentFrom.Text, out decimal cash) && decimal.TryParse(paymenTo.Text, out decimal cash1))
            {
                View.Filter = delegate (object item)
                {
                    User user = (User)item;
                    return (user.Payment >= cash && user.Payment <= cash1);
                };
            }
        }


MainWindow.xaml
<Window.Resources>
...............
        <DataTemplate x:Key="GroupTemplate">
            <TextBlock Text="{Binding Path=Name}" FontWeight="Bold" Foreground="White" Background="DodgerBlue" Margin="0,5,0,0" Padding="3"/>
        </DataTemplate>

    </Window.Resources>

........

<ListBox Grid.Row="1" Name="usersList" Margin="10" Padding="5 5 0 5" SelectionChanged="sex_SelectionChanged" ItemTemplate="{StaticResource UserDataTemplate}" HorizontalContentAlignment="Stretch">
            <ListBox.Template>
                <ControlTemplate>
                    <StackPanel>
                        <ItemsPresenter/>
                        <Button Margin="5" Padding="10 5" Click="ListBoxItem_Click" Content="dodaj nową osobę..."/>
                    </StackPanel>
                </ControlTemplate>
            </ListBox.Template>
            <ListBox.GroupStyle>
                <GroupStyle HeaderTemplate="{StaticResource GroupTemplate}"/>
            </ListBox.GroupStyle>

        </ListBox>