YOU SAID:

I think my sister is stupid and my sister thinks im stupid

INTO JAPANESE

私は私の妹が愚かだと思うし、私の妹は愚かなイムを考える

BACK INTO ENGLISH

I think my sister is stupid, and my sister thinks I'm stupid

INTO JAPANESE

私は妹が愚かだと思うし、妹は私が愚かだと思っている

BACK INTO ENGLISH

I think my sister is stupid, and my sister thinks I'm stupid.

INTO JAPANESE

私の妹は愚かだと思うし、妹は私が愚かだと思っている。

BACK INTO ENGLISH

I think my sister is stupid, and my sister thinks I'm stupid.