(note that i a doing coursework, and so i hv no idea about the paper3)
to get better in first language, well, you cant in such a short period of time. what would help would be to start to try and really deep-think the questions. go get tips like how to write certain essays, etc. honestly, i think there is no way to get better in english first language (second language would be easy, past papers help alot, if you dont get a* ur thick (for esl))... the only way some people r much better than others is because they have a much better grasp of the english language as a whole (like by reading alot of books earlier on)
actually, there is a way to get better grades. did you know that a huge amount of marks is allocated to the, like, data part of the question?? (for the 20 mark summaries, 15/20 are related to how much information you got from the text, one point, one mark style) make it a point to brainstorm and go through the whole article a few times before writing your summary/article/whatever... (paper 2 which i do is only directed writing and reading, everything is based on an article) go thorugh the article, and glean at least 17 points for the 20-mark summaries (usually 20 mark summaries have two passages-get 17 points from both, it doesnt matter if you have 13 from one and 4 from another, as long as they are set out properly, and the 13 are all main points, not details)
your writing style can be bettered in a fake kind of way by going through vocabulary lists. believe it or not, if you give in an essay without any proper vocabulary, you lose 10% of the marks. dont fret-alot of good vocabulary, grade 10 first language level can be gained from SAT vocabulary lists. every day from now, pick up a list of 15 words you had no clue about, and make sure you remember them. use words that are synonyms for more common words, dont go trying to remember words like papal, because u probably wont get anything about the pope in ur exam (i hope).
whatever...
business studies? i assume u have a problem with paper 2. the truth is, i do too... but i know exactly what the remedy is. go through your textbook/notes completely for business every day. read it, but dont test urself on it properly, just make sure u understand what ur reading (dont daydream). do this quite a few times (maybe five times) and ull perfect ur syllabus knowledge. now, you have to learn to apply it. go do past papers-about 10 years is enough for an a*, 5 years for an A. do the first half of them THOROUGHLY, properly. what i mean is, try to write the best answer you possiblly can, using as many resources as you can get. make sure you're getting full marks on every question. i advise u not to use the markscheme, as this does not always consider exceptions (ie untextbook-like answers). it is better to pose any serious questions to your teacher or tutor-you may be misleaded by people online.
after you do 3-5 years of perfected past papers, start doing them under exam conditions. use the 1mark 1minute scheme, where you allocate exactly one minute to each mark. never more, but sometimes less. do the rest of the papers like this, and identify where you have problems, which areas of the syllabus you are not perfect with. redo these with the help of your textbook, and then attempt the question(s) again, without any access to any resources. do not try to form an answer while accessing any resources-only learn what you did not know, and then go and try to write the answer seperately.
hope i helped,
good luck