YOU SAID:

i know a guy who is very dumb so i call him dummy

INTO JAPANESE

私は非常に愚かな人を知っているので、私は彼をダミーと呼びます

BACK INTO ENGLISH

I know a very stupid person, so I call him a dummy

INTO JAPANESE

私は非常に愚かな人を知っているので、私は彼をダミーと呼びます

BACK INTO ENGLISH

I know a very stupid person, so I call him a dummy