Did you purchase a paper questionnaire and the registration code came with it? In that case you have an account, that's purpose is to help you learn video-questions and variations and sometimes newly developed questions, which can not be viewed on a sheet of paper. You can learn all other questions on your paper questionnaire.
For this reason you can only take 5 exams in your FahrAPP.
You want more in order to prepare yourself better?
Ask your driving school for full access to FahrAPP.