Hello,
English textbooks are virtually useless. I understand my position may be somewhat controversial on a website that promotes textbooks for subjects like English Advanced. However, a subject like English cannot be rote learnt from a textbook as Legal Studies or Biology can. To obtain a 20/20 in any of the essay-based modules (latter half of commod, mod a and mod b), you need to have a strong voice and an implied position on each of your texts. This is an opinion that cannot be developed from textbooks.
My recommendation is that you use your teacher's resources, talk to your teacher as much as possible (literally become friends with them, that's what I've done and they are more likely to give feedback) and read up on a bunch of literary critics to improve your understanding of the texts. This will enhance your writing style and provide more direction.
To address your question about how to write essays (basically what you're asking), you need to begin submitting for feedback from your teachers. Textbooks are often written from the perspective of someone that did well in the HSC examination and presumably did well internally at their school. Whilst the Australian education system aims to be unilateral in its marking, English is an inherently 'subjective subject' and teachers have their preferences.
Also, there is no such thing as 'concepts' on how to write specific types of essays and how to respond to different types of questions. From the sounds of it, you need help with structure. There are some fantastic resources on this website, Bored of Studies, Ignite HSC's youtube channel (highly recommended), that all go through different types of structures and ways to approach long response questions. Furthermore, I think it would be worthwhile doing a bit more wide research on the aforementioned websites for exemplars and 20/20 responses. I accredit my success in English Adv (thus far) to reading exemplars and recognising the difference between a 15/20 and 20/20 response.