In accredited universities and college, lectures are principally held in German. There are a few exceptions, when the lectures are held in English. An overview can be found here >>>
International students studying in Austria must prove adequate German language skills. For graduate level studies, the language requirement is level B2 and in some cases level C1 (European language leves (CEFR). There are other qualifications that may be recognized, but for this information it is important to find out the details directly from the university.
University preparation programs in Vienna, Graz and Leoben prepare students for the targeted study programs. For such studies there are university entrance qualification, particularly for the subjects German, English, mathematics, physics, chemistry, biology, history and geography.
Information about German course providers, test dates, and opportunities to learn German on your own