i've a website done by joomla+soblad, and there's a page for registration form, but before you see the registration form you have to pick the type of the registration from a drop down menu, so how can that be done?
you can create parent form with subform for each type. Then in parent add dropdown with all types and group field for each subform and use conditionals to show the right group based on dropdown value.
You create a form in the content type (admin from, site form tabs). You will need to create 1 content type for parent and 1 for each type of registration, then you link them together using group field in the parent form.