急!!翻译成英文~申请书

Dear Sir or Madam:
Since I have to return after taking CET-4, It is possible to miss the professional curriculum on May to me; therefore, please approve me to postpone it on Augest.Thanks a lot !

Best Regards!

Sincerely,
XXX

用have to 表达 语气更加强烈，表示不可更改的，必须回国。

Dear Mr and Ms,
Since I will go abroad after taken part of CET-4, therefore, I am very worries about I can't join the major class in May, would you approve me join the classes in August instead of May? Thank you very much! Best wishes!
Yours Sincerely,
XXX

Dear Sir or Madam,

I will like to postpone my major courses from May to August, because I have to return to my motherland after my CET-4. I am not sure that I am able to be back in time. I hoped that the school will authorize my proposal.

Best regards,
(your name here)