The exam questions are based on the ECQB (European Central Question Bank), which is developed by EASA. Since the ECQB is property of EASA and its contents are confidential, these questions may not be published. Neither EASA nor Austro Control cooperate with third parties regarding the publication of examination questions.There are several textbooks that cover the material for each of the required exams, and these will be the centrepieces for your understanding of the topics. The books are published by a variety of publishers and your flight school will almost certainly have a preference as to which one you use, so it is worth speaking to them before investing in these books.
For more information on EASA's ECQB, see the following link: European Central Question Bank (ECQB) | EASA (europa.eu)