DAX help needed - context filter only for values in both categories

Hi,

Could you please help me with solving issue with DAX formula?

I created very simple dataset which I replicate my problem with main dataset ( sales data).

I would like to filter only for Groups which have sales in both Catogies ( there is "Category" column = Main or Discount). 

In the end, I am interested in table ( similar to the pivot table in Excel), but only for Groups which have sales in 'Main' and 'Discount'. I do not want to compare only 'Discounted" or 'Main' products, I would like to have a look only at both categories sales.

Many thanks,

Karolina