YOU SAID:

my dog ate my sister and then my sister ate my dog

INTO JAPANESE

私の犬は私の妹を食べ、次に私の妹は私の犬を食べました

BACK INTO ENGLISH

My dog ate my sister, then my sister ate my dog

INTO JAPANESE

私の犬は私の妹を食べました、そして私の妹は私の犬を食べました

BACK INTO ENGLISH

My dog ate my sister, and my sister ate my dog

INTO JAPANESE

私の犬は私の妹を食べました、そして私の妹は私の犬を食べました

BACK INTO ENGLISH

My dog ate my sister, and my sister ate my dog