How do I improve?

There are so many different ways to develop your English skills. However, the main two formats of this are: learning, and application. So, you need a basis of knowledge to make up any of the other skills, be cause that lets you 'unlock' understanding/comprehension, and a level of fluency/accuracy. Therefore, you need to make notes or mind maps or flashcards and start to learn the content for the text you are studying. Then, you can approach the phase of application which is just simply practise. Practise essays, practise questions, and looking at mark schemes after to learn from your mistakes when you have tried to apply your knowledge. This is where a level of review comes in that helps you see where your downfall is and allow you to tweak it so you can fully grasp it in the next essay you write/question you answer.