I also struggled with english in year 10/11/12 not for the same reasons as you I always found it interesting and liked narratives but I hated essays especially in class essays. My main tips would be for essays
1) Literally read good essays in sections to understand how it works and replicate it. The way they teach essays at school makes absolutely zero sense, you need to see examples to understand how they want you to answer the questions but also don't feel the need to copy it, there is more than one correct answer just find a way that works for you.
2) English atar notes book, I literally lived on the year 12 advanced one and it was my life raft I 'm not sure if there is/how good the year 11 standard one is but definitely look into it.
3) Make yourself write practice essays frequently. At first your going to be resistent to it and find it difficult but you just need to write, no matter if it's amazing or terrible just admit to yourself where you are and get yourself into a routine (maybe an essay a week during year 11 and every second day during the holidays?)
4) The short answer questions for the hsc and some of the exams on thsconline have recommended responses to short answer questions they'll stop you over thinking (I went from 12/20 in short answer to 19/20 from year 11 to year 12).
5) Improve your vocabularly. This is the last point because it's not super important if you already have a decent range however it can strengthen your analysis and make your writing stand out /if/ you use more technical/specific words correctly and sufficiently sparsely. I would read really strong essays from professional writers like george orwell and write down words that stood out or I didn't understand and write down the words and definitions in a book and try to use some of them in essays.
6) (bonus point) When I was starting year 11 and throughout 11 and 12 I was very stressed about not being able to motivate myself for such an extended period of time and hence put myself under so much pressure I wasn't really able to function. Really I recommend trusting yourself and staying calm and not comparing yourself to others (this is clichè but actually so true).
For your point on motivation I think though English isn't everyone's favourite you should definitely try to read a couple of books during the holidays they could be narrative or autobiographical just to get you more invested or give greater understanding to why we tell stories as I'm assuming (please correct me if I'm wrong) that your more of a science/facts sort of person. I guess seeing the ways English intersects with your interests might also help but I can't really help you there.
For speed of writing it really is just a matter of practice, considering you are still in year 10 you still have a significant amount of time to improve this, just writing your notes down in class by hand if they make you use computers, along with practice essays, I tried to keep a diary to help myself with writing a lot as well.
Anyway I hope this helps a bit
