What is the input and out of a form which contains multiple variable of complex type?

\Hello, Guys!
I'm new to Bonita BPM 7.4.1 and I really need your help.

business variables do not retrieve the values from the formOutput

I use several business variables to store values chosen by user interaction from UI forms.
After each task I want to use a business variable to store the user selection for a certain type and at the end of the process the last form is supposed to display the selected data from each tasks.