im a year 11/12 teacher in VIC. Teaching the amount of info you "need to know" for exams is disgustingly hard. I am so sorry that you are feeling this way and have to respond to the system by being overstressed this way. 2-3 hours is too much time. As a teacher, i study definitely over 5 hours a night to organise how I'm going to teach my classes and it never ever feels like enough when I get to class. It is a nightmare for teachers and therefore a nightmare for you students. It is very unfair.
My advice is LESS IS MORE. Keep short dot pointed notes. Key points. Definition, example, another example. Once you can put together shorthand notes, only then can you begin to link the ideas together. Anticipate practice questions and annotate the crap out of any practice questions, even textbook review questions and stuff. Don't go overboard with just reading and reading notes and highlighting. Short, simple, to the point. Try to keep things under appropriate sub-headings and check in with your teacher to make sure the subheadings are appropriate.
Prioritising is also key. It is so important to figure out when to study. Keep a very good diary and schedule in study with plenty of time before assessments.
Keep up a dialogue with your teacher. They are going to be one of your best resources for the next year and the rest of this one.
Be kind to yourself about marks and I'm general. Be kind to your teacher and be super aware of your classmates just trying to get by as well.
You are strong for asking questions and for even being here and looking to share and better your position. Keep pedalling. Get through.
Sending you good vibes. Oh yes and prioritise sleep!!! Makes a massive massive difference.