時制が難しい

学校英語で、文法はひと通り習得したつもりだけれども、いざ自分で英語を書いてみると、時制の選択に悩む。Lang-8でも、時制について添削された。
冠詞の"a"と"the"、単数形と複数形も悩むけれど、意外に添削されない。
上段が私の書いた文章、下段の青い文字が添削後。

When I have corrected Japanese by foreigners in Lang-8, I found it didn’t become natural Japanese because they quoted expressions directory from dictionaries.

When I correct Japanese journals written by foreigners on Lang-8, I find that their Japanese isn't natural-sounding because they quote expressions directory from dictionaries. --> (Better to have this sentence in a continuing action sort of tense rather than a past tense, i.e. you are describing an action that you regularly/habitually perform)

I guess I also did the same thing when I am writing English.

I guess I also do the same thing when I write in English.

I cut and pasted form a translation website, and it became unnatural expression.

I have cut and pasted from a translation website before and the resulting English was unnatural-sounding.