conditional logic in contact form

hi,
i bought your start up demo template and i didn’t find how to set up a conditional logic in your contact form.
To explain you a little bit more:
if my first question is : where do you live with 2 choices in a rawling list ( France or Germany) ?
i want that all my folllowing questions are different among the answer of the first question: if the person answers France, second question is do you live in a city ? 3rd question is do you have a dog ? . if the person answers Germany, second question is do you have a car ? , 3rd question is are you married ?…….

thanks for your support