Sorting in aggregation on mongodb?

Question

MongoDB

Hello,
The problem is as follows, there is the following structure in the database:
Tasks
Users
Region
Department
...
...

The received data needs to be filtered and sorted, but something went wrong when writing the aggregation, and either everything except sorting works, or it works everything, but one record is displayed instead of an array.
Does anyone have an example or parting words in which direction to google?
General essence: it is necessary to link 4 tables to dynamically filter and sort.