我已经写好了英文

I have already finished my homework. 这种译法更强调你写完了，而第一个解答更强调写的是作业。

I finished my homework.

I have finished my homework.

my two clasemates 应改成：two of my classmates, I think things like this will not happen like that if they could think of their friendship and calm down their mood这句应该是虚拟语气，应改成： I think things like that would not have happened if they had thought of their friendship and calmed down their mood. 此句 better communication also can help to solve the problem.也错了，also can 必须改成：can also

I have already completed the letter

i have already written the letter.