Well, I'm sorry to say but English is important, and it will continue to be through year 11 and 12, and it is critical that you do fairly well if you want good marks and ATAR and such.
I feel you're pain, I too have trouble with English. (I'm in Year 11).
First thing I'm going to say is that I can't give you any sample essays, you'll have to look them up and ask your teacher.
Next, do you know why you got the D? Was the outcome marked from an assessment you just did not do well on? Ask the teacher why/where you lost the marks, and what to do to improve.
(I despise my English teacher, he is a a rude arrogant man who can't teach, is impairing my learning and making not want to ask him any questions. So if I wanted to know why i did badly i would ask another English teacher (namely the head) someone I can stand and i understand. So remember, you aren't limited only your teacher for help).
Go back through the tests and assignments and look at what you did badly, and also what you did well (this can be based on common sense and comments/ticks).
You could try just going up to your teacher and asking them to help you.
Also ask your teacher for past essays, they should have some, hopefully.
Try expanding your vocabulary, if you don't know a word, look it up, (make sure you know how to use it in a senstence or when a perfect time comes to use you won't know how). Dare I say, when typing up assignments, use the Word 'Synonyms' function when you right click a word. Don't just click one that sounds fancy and use it. It is a computer making these terms, they might not fit! I suggest every time you see a word in the synonyms list that you like, or have vaguely heard of, look it up, when you think you know how to use it, then you can use it.
Time management is important, if you are doing your assignment at the last minute an don't studying for tests (not that you really have to in year 10, but at least fo the SC create a practice essay and story) you will not do well.
Good luck.
I hope I helped.
P.S. I am not going well in English... but that is mostly the teacher's fault. Thanks for asking.