Are you using a headset or over head speakers? Headsets will make a world of difference to understanding the RT.
Practice practice and practice. Knowing what is likely to be transmitted to you is half the battle. Sit with an instructor and go through the expected calls and when. Eg, taxi instructions won't be given to you when you're airborne.
Draw a circuit diagram and write in the calls you expect to make. Then what calls ATC will make to you. This will help you build the RT situational awareness. You have enough to do when flying the aircraft to also be figuring out in real time what's been said. "Armchair flying" is invaluable if you don't have access to a flight sim programme.
The speed of transmission makes a difference too. The Australian accent can be a challenge.
When you first fly to a different country, you'll possibly encounter the same thing. This happened to me when I first flew in Europe etc. I knew what to expect but the accented English was a struggle for a little while.
When you fly in the US, it's the speed of transmission as well as the non standard RT that'll catch you out initially.