Ответы на вопросы:
I understand you, because I have the same problem. I'm also very nervous before the tests. I drink special pills to calm down. Also I try to think about good things before exams.
I chose English for the exam, because I like to learn this language. And I think I'm good at learning languages.
I do a lot of grammar exercises, read books and watch movies in English to prepare for the exam.