唔該幫我cc依句英文句子文法有無錯誤

I would change the sentence as:

The objective of the class club is to organize activities for all the classmates so that we (或者"they", 視乎你用第幾身去寫) will be closer.

(activities 並不能用design 這個動詞, 如果想講「搞d活動」, 可以用organize, 或者hold some activities 都得)
(friendly, 意指別人和藹可親, 如果用來指大家「更好朋友」的話便不大適合了)

class club's objective is design the activities to make all classmates more closely and friendly together

class club's 其實意味有一個活動組識的成分 所以不用design the activities
可change為
the function(功能) of class union is to make all classmates more closely and friendly together

或用番class club's objective

都ok~~

英文句子文法其實是無錯, 但錯在ｓentence　ｓｔｒｕｃｔｕｒｅ

即是把中文直譯英文，變成一句不順暢的英文
所以不是一句好英文

The class club's objective is to design activities making all classmates more closely and friendly together.
class club: refer to one particular class club, add 'the'
is design:是設計
is to design:是去設計（用下者才合情理）
activities: talking about activities in general, no need article 'the'
making: after the word 'design', we use gerund rather than to-infinitive, this is the grammar rule

The objective of the class club is to devise and hold activities for all classmates in order to enhance their relationships.