so it return to 0 every date guess it is because the are some missing dates in between? any suggestions to make this a bit more like a normal time series?
The problem is that you have several Sales.quantity values at each date with a large range of values. The line between dates simply connects the last point of one date to the first point of the next date. Both values are usually low, though not always, as can be seen in the occasional diagonal line. Here is a graph showing your first 100 points.