I see. Lots of stuff going on there!
I would like to suggest that you become more familiar with concepts that will enable you to tackle your project better. Concepts like linking objects (data types), adding/removing list entries from list fields in an object, and other ones.
These series of short videos do a great job:
Here they are:
These videos deal with orders and items. In your case you have users and tasks.
Hope this sparks some ideas on how to improve the functionality that you are building! 