Custom / hybrid / dynamic Matrix

Hi all,

I am strugling to build a custom matrix, I have found some similar topics but I could not figure how to adapt it to my issue.

I already checked the following examples :

https://community.powerbi.com/t5/Community-Blog/Creating-a-custom-or-hybrid-matrix-in-PowerBI/ba-p/1354591 PaulDBrown 

https://powerbi.tips/2019/07/the-dynamic-time-matrix/

https://exceleratorbi.com.au/building-a-matrix-with-asymmetrical-columns-and-rows-in-power-bi/

All the examples above have 1 level column header calculation.

So here is my example:

Input data :

Table 1 from an excel sheet.

Table 2 from another excel sheet, which have the Label column in common

Output:

In Excel, it can be done with a basic pivot table (at least the part without the target).

The calculations for the columns are :

item = sum(No of Lines)

late = sum(No of Lines) - sum(Code Count)

percent = sum(No of Lines) / sum(Code Count)

The month should evolve dynamically (if there is a new data in a new month, the new month for the actual year should appear and added in the total calculation of the new year). (Like https://powerbi.tips/2019/07/the-dynamic-time-matrix/)

A variation can be proposed regarding the column header like the following: