YOU SAID:

Yeah I don't think he understands that either

INTO JAPANESE

うん、私は彼がどちらかを理解しているとは思わない

BACK INTO ENGLISH

Yeah, I do not think he understands either

INTO JAPANESE

ええ、私は彼がどちらかを理解しているとは思わない

BACK INTO ENGLISH

Yeah, I do not think he understands either