iXsystems said:

But how to change the units in this column from hours to Stunden, day(s) to Tag(e) and so on?

You can localize the unit of time tokens in the duration field's editor like so:

Infragistics.Win.UltraWinGanttView.Resources.Customizer.SetCustomizedString(
    "TimeSpanEditor_DayDisplayString_Singular",
    "tag");

Infragistics.Win.UltraWinGanttView.Resources.Customizer.SetCustomizedString(
    "TimeSpanEditor_DayDisplayString_Plural",
    "tage");

Each unit of time has a corresponding string resource, following the same convention as above, i.e., WeekDisplayString, HoutrDisplayString, MinuteDisplayString, and each has a Singular/Plural variant

iXsystems said:

Is it possible to install a context menu on dependeny lines?

You could handle the control's ContextMenuInitializing event and add a menu item for the dependency, like so:

using nsGVElements = Infragistics.Win.UltraWinGanttView.UIElements;

this.ganttView.AutoDisplayDefaultContextMenu = AutoDisplayDefaultContextMenu.GridAreaOrChartArea;
this.ganttView.ContextMenuInitializing += new ContextMenuInitializingHandler(ganttView_ContextMenuInitializing);

void ganttView_ContextMenuInitializing(object sender, ContextMenuInitializingEventArgs e)
{
    UltraGanttView control = sender as UltraGanttView;
    UIElement controlElement = control.UIElement;
    Point clientPos = control.PointToClient(Control.MousePosition);
    UIElement elementAtPoint = controlElement != null ? controlElement.ElementFromPoint( clientPos ) : null;

    nsGVElements.TaskDependencyLineUIElement lineElement =
        elementAtPoint as nsGVElements.TaskDependencyLineUIElement;

    if ( lineElement != null )
    {
        TaskDependency dependency = lineElement.GetContext( typeof(TaskDependency) ) as TaskDependency;
        IGMenuItem menuItem = new IGMenuItem("Dependency");
        e.ContextMenu.MenuItems.Add( menuItem );
    }
}