Working hours considering overlap times

Sorry for the delay, I was out of office on friday.

Responding to your questions:

OK, so the real working hours would be the sum  of (End_Time - Start_Time) for all activities per user and day, correct?

- Correct, but the problem that I have is that if one person performs 2 or more tasks durning the same (or part of the) time, I should only consider the amount of time once, but sum the total SKU's processed.

do you have data on several days? (I guess so)

- Yes i do, usually I work this data on Excel on periods of 5 days (weekly data) or 20-22 days (monthly data)

Can you show the structure of the tables in your model (in yo do not share the pbix)? 

I tried to make something on power BI but it ended being pretty messy, here is part of the raw data extracted from the data base:

For example, for task 1, 2, 3 and 9 they were done by the same "USER1",

therefore i should add the total amount of time worked (end - start date) but without the overlaps. which would be 14:59 - 14:17 = 42 minutes.

Besides, in total he worked over 7 SKU's, so the productivity would be 7 / 42 (skus/min) -> 10 sku's per hour

On the other side, for USER2, he did 2 tasks without any overlap, so the total time would be the sum of the working hours.

And therefore the productivity would be:  (1+2) /( (14:52 - 14:40) + (14:35 - 14:25))

Once again thank you for your help!