Need help on How to add/remove from a List issued from a dropdown item

I tried just for fun to create my own list of users with the ability to select a company and have the app display the Users associated to that company . What I have not been able to do at this point is how to display managers of a company based on my selection from a dropdown list value of users. Everything seem fine, no errors noted but nothing appears in the database therefore nothing show up in my repeating group created to display the managers I have selected when I run the app. seems weird, not sure why. Here is the link to my quick app :

Thank you.