Greetings from Syncfusion.
We have analyzed your code and we suspect that your requirement is to show the day of week in axis labels. You can achieve that by setting IntervalType as Days and Interval as 1. Please refer the below code.
XAxis.IntervalType = Syncfusion.SfChart.XForms.DateTimeIntervalType.Days;
XAxis.LabelRotationAngle = -45;
XAxis.Interval = 1;
XAxis.Minimum = start;
XAxis.Maximum = end;
XAxis.LabelStyle.LabelFormat = "dddd";
If your requirement is different from the above solution. Please provide an exact requirement of yours and please share the screenshot. This will be helpful for us to provide a better solution at the earliest.