Struggling with basics [JEE Mains repeater]

I'm a state syllabus student and we have never been taught NCERT textbooks. So when I'm sitting in the Quadratic Equations class today, I see the students next to me (lifelong CBSE students) able to easily solve questions with the teacher's hints. While I can't follow the question because the teacher obviously skips over calculation and basics that I've never been taught. How do I counter this? I can read NCERT sure but it's gonna be time consuming compared to someone who studied from NCERT in +1 and +2. I know because I only used NCERT textbooks for Biology in +1/+2 and I can answer any question from any corner for that subject. But to read Physics NCERT for the first time would mean I have to explain everything to myself by what I know and even a single page can take 30 minutes. So skimming through NCERT before classes is time consuming (but not time waste as far as I know). Another option is to just do PYQs and learn concepts/pick up speed along the way. But I'm not sure if that's gonna work and I sure won't be able to see any results quickly. Can anyone who has been through this struggle help me?