There are some concepts that I didn’t understand. I overcame this by joining a discussion group, that way, I got to exchange ideas with other students and could find other students that were really good at what I was struggling with and vice versa, so discussions can be helpful.
I had problems with chemistry early on in high school. Chemical equations, their rules and the formulas in calculating concentrations etc. My attitude towards chemistry was also not good, I thought it was too difficult. What really helped me was putting it some extra effort in understanding the basics of these concepts, and working in groups to help each other. A group could be formed by at least 2 people. Also trying out exercises in text books helps. You could also try online exercises.
I struggled with understanding some concepts in physics particularly. I sought out the help of my teacher and used to do additional exercises outside of homework to practice more. In addition, I formed a study group with friends who were doing well in Physics to be able to understand how they explained concepts. This really helped improve my understanding and the consistency of practice and exposure to different physics questions led to me enjoying physics in the end. So it wasn’t that it was difficult, I just needed to get over the mental block that physics was difficult and find tools and ask for help to improve my grades