Hi there!
I am creating an app for registering the new events requests by the users.
I have a dropdown menu (Event Subtype) which is dependent on another dropdown menu (Event type).
I want to create an interactive form that contains mandatory fields, while the fields appearance is dependent on the dependent dropdown menu choice!
see screenshot below for a clear imagine.

When the user choose a certain Event Subtype, certain fields will be visible for him and so on.
I tried the following formula but I get an error which I can not understand.

could anyone pleases help me achieving my goal?
thanks in advance.