主题：【求助】写了一封离职告别信，高手们帮我把把关！ -- DF41

你改的比他原来的还要糟。

may后面带Present tense，所以是may already know或may already have known.

so much是特殊句式，一般用法是XXX so much, that xxxx比如：He ran so much that he sprained his ankle.

Upon一般用于条件，如：He left upon receiving the news。

leave 后一般直接带noun。

it指代什么？

will be也不对，应该用present tense

改正后是这样

As some of you may already know, I have submitted my resignation to XXX on Jan.06 and this is my last week here.I have enjoyed working with you very much, and I am leaving here with a mixture of excitement and regret. You've not only been colleagues but dear friends as well.

学语言要注意输入（听读）与输出（说写）的累积，不能光学语法。特别是英语；英语的语法本来就很混乱，没有实际中的运用，是怎么也学不好的。