If you create multiple v6.x forms on a task you need to add "Next" and "Previous" widgets to allow navigation between the different forms. You should add one submit button on the last form.
Also I would rely recommend to use v7 forms as they includes tons of improvements (especially related to dynamically display/hide content) and also will be supported for a longer time frame.
Please avoid to post a comment such as "please, i need help !!!" (I think this Stack Overflow comment rely explain why). If time is key for your project I always recommend to consider getting in touch with Bonitasoft for consulting.
@antoine.mottier can you elaborate the implementation for Bonitasoft v7?
I am thinking something like: create a form in the UI Designer, add all the necessary input widgets and the submit button. Create also a button that will change the value of a variable. The value of this variable could be used in the expression for the 'Hidden' attibute of widgets. If so, what type of 'Action' should this button be? and what the url?