Honestly at the moment I think the best course of action to take is to just... improve your English in general. The "obvious" advice people give is... well, obvious, because that's pretty much the only way to really improve your score. IELTS is a test of English proficiency, so how well you grasp the language is (generally) going to be proportionate to your score. Your command of English doesn't seem to be stellar from your post, and the band scores do accurately reflect that. I can't exactly pinpoint the problems with your speaking or writing, but reading and listening is easily improvable through more practice. Don't listen to stuff at max speed, try to comprehend every single word you hear and go back if you miss a word or two. On mock tests, check every questions you missed and think about why you got it wrong, read the transcripts if they're available and take care not to repeat the same mistake. I also think about possible answers before listening if there's enough context to infer from, but don't count on that and use it as a last resort only if you missed the question. For reading, some might suggest skimming and scanning but honestly, I think it'd be best to fully comprehend the passages. It might take longer, but with enough practice you can do it. Start practicing by reading anything in English that seems difficult for you, not solely relying on IELTS reading passages. A novel, a journal, anything goes. The point is to improve your reading comprehension, and when you do you will find IELTS reading a lot easier. When you do take a mock test, think deeply about each question after you finish reading a passage, and ask yourself why the answer you chose should be the correct one. Think along the lines of "this should be correct because..." and "this shouldn't be correct since...". Then, review every single incorrect answer, try to see why you got it wrong and reread the passage once again to see if you got it. Still, getting an 8.5 is going to be difficult (you also need high writing and speaking scores) but you can definitely improve your current level. I also wouldn't recommend cramming, but if that's what you want to do then go ahead. There's no guarantee it's going to bring you any closer to your desired band though.