YOU SAID:

Jaehyun couldn't sleep very well last night, so that's why he didn't come to class.

INTO JAPANESE

昨夜はジェヒョンがあまりよく眠れなかったので、授業に来なかったのです。

BACK INTO ENGLISH

Jehyun didn't sleep very well last night, so he didn't come to class.

INTO JAPANESE

ジェヒョンは昨夜あまりよく眠れなかったので、授業に来なかった。

BACK INTO ENGLISH

Jae-hyun didn't sleep very well last night, so he didn't come to class.

INTO JAPANESE

ジェヒョンは昨夜あまりよく眠れなかったので、授業に来なかった。

BACK INTO ENGLISH

Jae-hyun didn't sleep very well last night, so he didn't come to class.