Hi Arwa,
It's wonderful to hear that you are able to understand a lot of the content from English media. I believe that means you have built some good vocabularies and your listening/ reading skill is strong. However, academic writing is a different skill that needs practice. You probably notice that we don't always write exactly what we say (except for social media and texting!). It will be helpful for you take some structured class that teaches you English sentence structures and conjunctions. Most importantly, try to apply them as frequent as possible. For your spelling, you can definitely get help from a teacher. At the same time, turning on spell check will help - don't just accept all the changes, but pay attention to your errors and don't repeat it again. Hope that helps and please be in touch if you need.
All the best to your tests and school application.
At first glance of your concern, I would consider vocabulary learning might be the point that can help you with academic learning. It is important to note that academic writing requires good command of academic terms to describe complex situations and these terms are less used in everyday conversation. Do not just learn by heart with no practice. Please be sure you apply these words as frequently as possible. Most spellings (>80%) are of regularities in accordance with pronunciation, so as soon as you can pronounce the word precisely, you can spell them well and certainly can lessen your memory load in the learning course of vocabulary.
Furthermore, if you cannot well make use of conjunctions such as and, or however, which ...etc, you may refer to a grammar textbook to master these skills. That must be a simple task for you to achieve in few weeks.
