Hi Manal,
In short you need to have the two axes share the same axis zone level which is achieved by setting the CreateNewZoneLevel property of the Anchor to false, then you need to have another axis that shows the title at the center - for example:
   NCartesianChart chart = (NCartesianChart)nChartControl1.Charts[0];

    NBarSeries bar1 = new NBarSeries();
    bar1.Values.Add(10);
    bar1.Values.Add(20);
    bar1.Values.Add(30);
    bar1.Values.Add(40);
    chart.Series.Add(bar1);

    NBarSeries bar2 = new NBarSeries();
    bar2.Values.Add(10);
    bar2.Values.Add(20);
    bar2.Values.Add(30);
    bar2.Values.Add(40);
    chart.Series.Add(bar2);

    NBarSeries invisibleBars = new NBarSeries();
    invisibleBars.Values.Add(0);
    invisibleBars.FillStyle = new NColorFillStyle(Color.Transparent);
    invisibleBars.BorderStyle.Width = new NLength(0);
    chart.Series.Add(invisibleBars);

    chart.Axis(StandardAxis.PrimaryX).Visible = false;

    NAxis xAxis1 = ((NCartesianAxisCollection)chart.Axes).AddCustomAxis(AxisOrientation.Horizontal, AxisDockZone.FrontBottom);
    NDockAxisAnchor dockAnchor1 = new NDockAxisAnchor(AxisDockZone.FrontBottom, false);
    dockAnchor1.BeginPercent = 0;
    dockAnchor1.EndPercent = 50;
    dockAnchor1.CreateNewZoneLevel = false;
    xAxis1.Anchor = dockAnchor1;

    bar1.DisplayOnAxis(StandardAxis.PrimaryX, false);
    bar1.DisplayOnAxis(xAxis1.AxisId, true);

    NAxis xAxis2 = ((NCartesianAxisCollection)chart.Axes).AddCustomAxis(AxisOrientation.Horizontal, AxisDockZone.FrontBottom);
    NDockAxisAnchor dockAnchor2 = new NDockAxisAnchor(AxisDockZone.FrontBottom, false);
    dockAnchor2.BeginPercent = 50;
    dockAnchor2.EndPercent = 100;
    dockAnchor2.CreateNewZoneLevel = false;
    xAxis2.Anchor = dockAnchor2;

    bar2.DisplayOnAxis(StandardAxis.PrimaryX, false);
    bar2.DisplayOnAxis(xAxis2.AxisId, true);

    NAxis xAxis3 = ((NCartesianAxisCollection)chart.Axes).AddCustomAxis(AxisOrientation.Horizontal, AxisDockZone.FrontBottom);
    xAxis3.Visible = true;
    xAxis3.ScaleConfigurator.Title.Text = "Some Text";
    invisibleBars.DisplayOnAxis(StandardAxis.PrimaryX, false);
    invisibleBars.DisplayOnAxis(xAxis3.AxisId, true);

Best Regards,
Nevron Support Team

Hi Manal,
You need to specify that the axis scale is inverted - this is a property of the scale configurator:
chart.Axis(StandardAxis.PrimaryX).ScaleConfigurator.Invert = true;
Hope this helps - let us know if you meet any problems.

Best Regards,
Nevron Support Team