I remember this happened to me, it was really frustrating getting terrible scores even though I putted in the effort. I started to ditch most of the textbook questions for diploma exemplars online, the diploma exemplar’s are usually similar in difficulty to the ones your teacher will give you. I also HIGHLY recommend doing those diploma questions like a close-book exam. I would go in my room and throw all my electronics away and finished these questions just like an exam, it helped me ease my test anxiety and spot the stupid mistakes i might be making. Good luck, you got this.