You try your best; give more time than anything else.
Read other books & news papers in English. Listen news on radio & T.V. to learn English.
But do not run after O level. When you come in higher study group later on, all will be equal.
So why waste your talent and money. They charge very high fee as well. You will be surprise to know that now this system is being discarded by the developing countries. It is not used there.
Look at us we adopted. Do not push your self for this study.