Greetings! It would not be bad in the Calendar section for each user to enable the view of completed tasks without taking due date into account. That is, I completed 5 tasks on July 21, and I see them in the calendar placed in the square on July 21, although due date may be July 25. The next day I completed 2 tasks, and I will see them on the calendar on this date. Then each user will be able to see how much he has done in total, for example, in a week and evaluate his productivity, whether there is a due date in the task or not.
In the List section, you can see what was done in the week, but to the right of the task you never see the task completion date, only due date.