1 X axis from multiple sources

What you need to do is to create a separate calendar table, to which you will connect the table(s) via the create and finsih date. If it all comes from one table, one of the relations will be unactive and you will activate it with use relationship in the calculation.  
If created and completed comes from two tables, you just simply both map it to the date table. 

Next you put the weekn number into the X-axis and the calculations into the Y axes. 

To do this, study a little about date tables and how they work https://www.youtube.com/watch?v=_n6iIqm_CKE
and about how to use userlationship() when working with multiple date columns in one table.