Hey,
This is not the thing to be stressing over during your prelim exams (or anytime really). You can definitely improve between now and the HSC by a lot. Tbh, year 11 does not count towards your atar and the majority of your subjects will have completely different content (not really sure what subjects you do but my content was different for everything, however the skills stay the same).
There are a lot of resources available to you that you can use (make use of your teachers-they will definitely priorities you over any of the junior years and I found that in yr 11/12 my classes had a much better relationship with our teachers, libraries are amazing for both studying and books/resources, Atar Notes (ask/answer questions, essay marking, notes, nerdy but this is one of my favourite websites atm), whatever else that you can find helpful). Your answers and marks should definitely improve if you are motivated and put the effort in to study. Even just by doing some practice essays and questions and handing them in to your teachers for feedback.
I don't really have an amazingly inspirational story to share with you. My ranks/marks have stayed pretty similar over the two years-however some have increased and others slightly decreased.
Slightly unrelated & probably not relevant to you-but for maths I initially started doing 2 unit and dropped at the beginning of this year to general. Last year my yearly mark (2 unit) was 54% while my trials this year (General) was 92%. While this may not apply to you and I definitely don't recommend you to drop down in Maths/English (unless you need to, I had to learn the entire year 11 content in the Christmas holidays), being in the right level course and putting effort in should work out for you (in all of your subjects really).