As you have said that you’re choosing maths in the future then you should take a challenge to face it. Maths becomes the most realistic subject if one is interested. You know your progress while solving the questions. Everywhere extended topics are being taught and no weird if you’re learning them also. Don’t wait for tomorrow to learn these topics and Insha Allah you’ll overcome the problem. You should talk to your teacher without hesitation about your progress going on. Don’t think that you’ll not get good marks. But if you’re really anxious then check your results and delay it for the next year.