Creating a cumulative bar chart with additional categories

So i have basically done what is asked for in this post but as a bar chart:
https://community.fabric.microsoft.com/t5/Desktop/Problems-with-formula-for-creating-cumulative-counts-for-a-Task/m-p/3374379#M1123304
This works for me

Now in my table are multiple subcategories for each entry which i also want to include in the visual.
For example if my table looked like this:

(The total is also the key attribute)

The visual i currently have would be this:

But i want to see which department is responsible for which part of the monthly amount. So i try to add the subcategory as legend and this happens:

Since some departments dont have any impact in april the acumulated values also dont get added to the sum in april.
How can i always keep the complete cumulative value in each month and also show the subcategories?

If anyone could help it would be greatly appreciated!