Pivot charts - data disappear after selecting or data are static
 

Hello

I'm just learning to work with Pivot tables and charts. I have the following
question:

I have a dataset with some columns, let's say one with 'Date' the other
three 'column 1', 'column 2' and 'column 3'.
I made a Pivot table of these. Put 'Date' in the row and the other three in
the column as 'sum of Column'.
When I make a graph of these, the legenda is either static and I cannot
choose just to show 'Column 2' for example of to show all Columns; or when I
can choose than after choosing all other columns disappear, in the graph as
well in the linked table. Very strange...
Another thing is that when I have negative numbers in two or more columns,
the Pivot graph (chart type is Stacked Area) only shows the negative numbers
of one column (it is not a Y-axis scale problem).
Please help...

Thanks guys!