Hi Geert,
Welcome to QSM Pro Support Forum. Hope you are having a nice day.
If you have set up contact fields for the particular quiz, those fields will appear either at the beginning or at the End of the quiz(displaying them either at the beginning or at the end of the quiz can be changed at the Options tab).
Though while setting them up, you can make them ‘Required’ by checking the checkbox for those fields. If you don’t check the ‘Required’ field then it will not force the users to enter their contact details.
Hope this resolves your query.
Regards,
Kriti