这应该是信吧?首先开头要有时间和DEAR_______.
几处语法错误：good at 只能就doing.（I'm good at sdudying）
like to take with classmates（此处缺主语,take应改为talk.）
My deskmate does study hard（does study连续两个动词出现,明显错误.应去掉does,study+s.）obey school rules（obey+S）
His charcter isn't sunny,which make him too shy to communicate with people.（连接词错误,如要用which应放在charcter后,此处应用it ,后面的make+s）
he will lose his temper sometimes when meeting some incidents.(此处的will lose不合理,说的是他的性格,也就是平常的状态.故应用一般现在时（loses)
what I should do to improve our relationship(improve用在此处不是很恰当.应改为make .better）
结尾处应对他/她表示感谢如：THANK YOU FOR YOUR HELP
祝语
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