Please believe me it was an accident that I do bad in this exam, so it doesn't prove I am not focus on my study or I am stpid further.
前一句it形式主才能引从句,后面要用连接词,否定句两个并列句间用or,“更”可以用further缀在其后表示。
Please believe that my failure in this quiz was an accident,which cannot prove that I didn't work hard ,or I am stupid.
Please believe that I didn't do well in the exam is a mistake, does not represent me not to study hard, but can not represent my stupid.