In Austrian universities, as well as in German universities, there are preparatory departments or so-called dt. Vorstudienlehrgänge. This preparatory department exists only for those foreign students whose school certificate does not allow them to enter Austrian universities directly due to the strong difference in school curricula, or due to the fact that Austrian students attend school for 12 years, and in some countries only 11 or even ten.
Austrian preparatory departments so-called Vorstudienlehrgänge exists in only 3 universities in Austria, the University of Vienna, Graz and Leoben (technical field). Admission to these preparatory departments is possible only through one of the Austrian university. So, you first apply to an Austrian university for the specialty you want to study. Then the Austrian university gives you admission to the preparatory department, in the admission to the preparatory department the university tells you which disciplines you need to study in it, and from which disciplines you need to pass exams to be admitted to study at an Austrian university.
A studying in the preparatory department lasts 1-2 semesters. In the winter semester, a study begins in October and ends in January (the so-called winter semester), and in the summer semester, a study begins from March to June (the so-called summer semester).
The cost of studying in the preparatory department is a small 370 - 400 euros per semester.
You can repeat each exam that you take in the preparatory department no more than 3 times. In addition, you have the right to take the exams that you need to take in the preparatory department externally, not studying in the preparatory department, which will save you a lot of time and money.
Moreover, a very important point is the fact that you will not be able to enter the preparatory department at an Austrian university without knowledge of German. You must speak German at least at level B1, and preferably at level B2, as currently most refugees in Austria study German in the preparatory departments of Austrian universities, so the opportunity to learn German in this place for foreign students is very limited.