Registering for FahrAPP you have to decide to choose between "First application" and "extension". This influences the composition of the exam and the number of exam questions. If this is your first drivers license please choose "First application" (Ersterwerb). You will then get 30 questions displayed in your exams.
Do you already have a drivers license and you're applying for an additional one? Then choose "extension" (Erweiterung) during your registration. You will then get 20 questions displayed in your exams.
Remember: Mofa is not a drivers license.
If you chose the wrong license type please submit a ticket.