It sounds like what you're saying is that you're finding it tough knowing how to get started on the questions, you're not sure what is being asked or what method to use. In this case, it's easy to feel lost if you're trying to do entire papers, because you're just encountering one thing after another where you don't know what to do.
So one thing you might try is to narrow your focus on just one part of the course. Try using VicMathsNotes exam questions organised by topic:
https://vicmathsnotes.weebly.com/year-12-specialist-maths.htmlThis way you can start to see patterns in how VCAA ask questions on the same topic, and that will build your ability to interpret the questions and know how to proceed. Make sure you also make notes on the things you find difficult, because that helps to more efficiently target your areas of improvement. Just gradually work through the topics, improving on one area at a time, rather than mixing them up.
Once you've gained experience with a range of topics and have more confidence with how to answer the questions, then move on to doing entire papers, where all the topics are mixed up.