Ответ:

  1. stay in ... for a year — live in ... for a year
  2. have a job at the University — work at the University
  3. an article about my experiences there — an article about what I experienced there
  4. lots of interesting subjects — many interesting subjects
  5. study unusual subjects — learn unusual subjects
  6. specialise in two or three subjects — concentrate on two or three subjects
  7. have a good time — enjoy yourself
  8. enjoy my time at school — like going to school
  9. decide what subjects interest you most — choose the subjects you like best
  10. start school — begin school
  11. leave school — finish school
  12. take exams — sit exams
  13. go to university — enter university
  14. start your preparation for GCSEs — begin preparing for GCSEs
  15. study chemistry — learn chemistry
  16. do practical experiments in the laboratory — carry out laboratory experiments
  17. it’s very different from Russia — it is unlike Russia

Более идиоматичные выражения из текста: have a good time, enjoy my time at school и go to university.