Sorry to hear you’ve been struggling with Physics. I did too at high school. Physics deals with lots of tricky concepts, that can take time and effort to understand.
Some schools require you to meet a certain level of achievement at L2 to grant entry, others don’t. I assume you know how this works for your school.
In my experience, students who demonstrate merit and excellence in the external papers in other sciences as well as maths often have the work ethic necessary to succeed in Physics. However a strong grasp of L2 Physics is certainly going to provide the foundation to support your learning at L3.
If you’re worried you won’t meet entry requirements, you could ask if your teacher would allow you to continue to work on L2 Physics in your own time over the summer, then give you a test to sit in February. If this is an option, discuss which papers they would want you to prioritise. They may depend on what is taught as part of a L3 Physics course at your school.
You might also be able to find a private tutor to help your understanding. Your teacher might know of some in your area. You should discuss this with your parents/caregivers as this option will likely have a cost. Some schools might grant a struggling student entry to L3 on the condition they continue their learning outside of school.
Another option would be to enrol in Te Kura over the summer (either this summer or next). They offer some standards that could help reinforce your understanding, and give you a chance to gain more credits in Physics.
You could get a L3 Physics workbook and find many of the great free resources online. If you have access to a learning platform like esucation perfect, this would be a useful resource for you too. Work on these in your own time to build your understanding. Your teacher might give you a chance to demonstrate understanding to gain entry into L3.
Even if you can’t take the course, your school might let you sit the NCEA exam. I’ve had students that couldn’t take Physics due to timetabling issues. With a good deal of work outside of class they have still succeeded in the exams (they were very motivated).
If all else fails, you could ask your chosen university about a bridging course. This would help you meet the required level of understanding even if you hadnt conpleted certain requirements while at school.
Best wishes. If you need any further advice, or clarification of anything I’ve said, let me know.