Given this information, I believe that your current position would be consistent with an ATAR within the range of high 70's (more specifically 76) and low 80's (up to 84). Of course, it is important to note that such estimates are far from decisive.
Your performance in English Standard is excellent and is highly likely to make a positive contribution to your ATAR. Since you are ranked first, your Assessment Mark (the mark that reflects your internal performance) will be adjusted to equal the highest Examination Mark (i.e. HSC exam mark) of any student in your cohort. If you end up achieving the highest Examination Mark, then that will simply become your HSC mark (final mark). Hopefully, you did well in your English Standard HSC exam.
The same can be said, although perhaps to a slightly lesser extent, about Studies of Religion II and Biology. Your performance in these two subjects is also likely to make a positive contribution to your ATAR. It is therefore important to prepare for these subjects' HSC exam to the best of your abilities, so that you can maximise your performance, which will increase your chances of achieving your desired ATAR.
On the other hand, Mathematics Advanced and, to a lesser extent, Chemistry, appear to be your lower-performing subjects. Because of this, you should do your utmost in preparation for your Mathematics Advanced and Chemistry HSC exams, which will hopefully lead you to perform at a higher standard in your exams.
I hope this helps!
