Essentially, given the nature and difficulty of Mathematics Extension 2, it would be reasonable to suggest allocating as much study time as possible towards this subject, while being mindful of your performance in your other subjects. Mathematics Extension 2 is a more difficult and challenging subject than Mathematics Extension 1, although your rank in Mathematics Extension 1 indicates that you may be able to take and perform well in Mathematics Extension 2, assuming that your cohort is academically capable given your school rank, and assuming that you are part of a large cohort (for example, being ranked in the 30s in a cohort of 50 students may be interpreted as less advantageous than being ranked in the 30s in a cohort of 100 students).
If you are interested in taking Mathematics Extension 2, it would be better to take it and give it a try than not to take it at all, leaving you to wonder whether you would have been able to perform well, had you taken it. Subsequently, you can determine whether to keep it or continue with Mathematics Extension 1 based on your performance in your tasks. Doing so would allow you to make an informed decision, compared to not taking Mathematics Extension 2 at all, in which case you can only make speculations.
I hope this helps!