To me, english is just knowing what the examiners are looking for and giving it to them. Naturally, i'm average at english, but I do well because unlike most people, I know how to interpret questions, structure essays, analyse texts etc. Work on your essay structure and exam technique for the rest of the year and see if you improve. You should stay in advanced until your last opportunity to drop.
Like at my school, in term 4 last year we did our AOS, so any kids who wanted to change from advanced to standard or even the other way round could up until the end of the first term of year 12. If your school does not structure it like that, you still have till the end of year 11. If you still feel like you are struggling after putting in more effort then consider dropping to standard, but if I were you I wouldnt drop without knowing that there is no way you could have done better than you are.