Don't fret English is easy and you will be able to get the grades you want. 

I got an A in one mock and A* in the other mock 

Here are some tips: 

Reading and writing: 

I know this sounds cliche but the more you read and write the wider your vocabulary, the better your skills and the more concise you are. ( I put bold on concise because it's CRUCIAL to be concise, if you are concise you will sound much better so be concise as far as possible  ( not to the extent you lose the metaphor you had in mind for one word because using similies and metaphors shows that you are capable in English and you will get a higher mark for using them [but ofc use them in the RIGHT context]) 

If you need to brush up on grammar such as  My friend and I went shopping vs my friend and me went shopping PLEASE PLEASE do and if you are still getting taught grammar PAY ATTENTION! 

When you read a book, make a list of unfamiliar words that you encounter. This would widen your vocab. 

Also, there are MANY reading exercises online which I advise you to do 

Speaking: 

It's a fairly straightforward paper. It just needs confidence ( like you don't need to be a savant on the topic you are speaking about, like they say it ISNT a knowledge test). 

There are videos online of people speaking which you can watch to get an idea of how people do these tests. 

To practice I used to take the prompt, mull it over for 3 minutes and start speaking into a voice recorder. I know I didn't get feedback but it was good practice and helped to ease my nerves about the whole thing. 

 Listening: 

Practice listening to a variety of accents and do whatever you can to boost your attention 

Also try to be RELAXED and NOT nervous 

So that's all I have for you today and here a few videos as well 

PM me if you have any questions 

https://www.youtube.com/playlist?list=PLMyv3FTQuVzK09Ac6cHm_GBfSZgQH0WbP 

Very useful 

There are also other channels out there