Some homework labs has lots of details. To solve it exactly takes time. But not the topic of the lab. I spent much time to gather info out of course lab. Is there any way to understand it step-by-step?
I understand few labs in MongoDB Aggregation Framework course are difficult to solve as they take a lot of time to figure out the pipeline as expected in the question.
I would recommend you to go through MongoDB Documentation for more details on stages and operators: https://docs.mongodb.com/manual/aggregation/. This would also give you an exposure to more examples.
If you are facing difficulty in understanding any particular lab, we can have a detailed discussion on it.
Please let me know, if you have any questions.