How to improve your vocabulary
Read articles on speedy paper website. Pay attention to the words the authors use to describe the same topic or problem. Write out synonyms.
Play a game like Alias in English with friends. The facilitator describes a term or concept in other words to the participants and they try to guess what it is.
Use Key Words For Fluency at the Upper-Intermediate level. There are a lot of words in there that you can use to talk about topics such as benefits, advantage, problems, and solutions. You can also take speech patterns from there.
How to improve your literacy
Turn off the spellchecker. Automatic correction prevents you from seeing and analyzing your mistakes.
Write by hand, it activates motor memory. Write difficult words several times.
Read in English. It activates your visual memory.
Choose a more familiar variant of writing (British or American) and stick to it.
How to practice the essay format
Write 1-3 essays a week on topics from the codifier or from sample USEs.
Read sample essays for the TOEFL American language test. You can find them on Google by searching for TOEFL sample essays.There are many similar topics and uncomplicated vocabulary. The overall structure of the essays is different, but the paragraphs with pro and con arguments are similar.
Analyze other people's essays by checking them against the exam criteria: number of paragraphs, words, adherence to style. For example, you can exchange practice essays with friends.