The official language of Austria is German, and it’s the most widely spoken language as well. Unofficial and less common languages include Alemannic and Austro-Bavarian.
English is widely spoken throughout the country, however, so you probably don’t need to rely overly heavily on Google Translate. However, there are times you’ll find yourself out in the countryside or other remote places, in which case a command of German may be helpful.
Make sure you have a good data package or go old school and bring a simple phrasebook for travelers.