First is pretty much essential for Standard English. As for your essay that is coming up, review what you did wrong in the previous task and ask your teacher for advice in that aspect, take a look at some guides on BoS for English, do a lot of practice essays and hand them into your teacher in order to get feedback and improve or make a very good pre-prepared essay through constantly handing it into your teacher and refining it.
It may be beneficial to have a chat to the top student of advanced or some advanced teachers to get advice, this helped me out tremendously
You will only get good at English through constant effort and devotion to the subject, so make sure to not get demotivated by one bad grade