Studying in Australia is an excellent opportunity to improve your English, but you need to practise your English in as many ways as possible:
Make friends with other students, both local students and those from other language backgrounds to yours.
Watch movies or TV in English and listen to music with English lyrics. Sing along!
Be prepared: read notes and look at any presentation before class so you are more familiar with the language used.
If you spend a lot of time with students who speak your language, agree to set times when you only speak English.
Set a goal to ask a question or speak up in each class.
Join a club, attend events, or join a sports team with English speakers.
Find work in an English-speaking workplace.