1: Always state what version your uploaded workbook is. I think yours is 9.1. I had to try several versions before I didn't get an upgrade message. If I just let it upgrade to the version I want, you probably won't be able to see the solution I show you.
2: I think something is wrong with your workbook. It opens on any of the upgraded versions, but Tableau bombs out when I open it on 9.1.
3: I can show you what you need to do, but we'll need to get a file that I can open, and that you will be able to open once I show you what you need to do.
And looking at this in 9.3, here is what I would do:
A: Don't use a quick filter. You lose all the other quarters because they get filtered out. Create a calc that looks something like this:
lookup ( attr(datepart('quarter', [Order Date] )),0)
Using a table calc to filter will still leave all the underlying table rows in the table for the sheet. User will still be able to select a quarter, and only that quarter will get displayed by the filter, but you'll still be able to access the prior quarter's data for comparison.
B: Access the prior quarter total using LOOKUP( SUM([Sales]), -1)
With that, you can do the math you need to do.