YOU SAID:

mads has a small you know thing

INTO JAPANESE

マッズがいる事を知っている小さな

BACK INTO ENGLISH

Know that Mads are small

INTO JAPANESE

マッズが小さいことを知っています。

BACK INTO ENGLISH

I know that Mads is small.

INTO JAPANESE

私はMadsが小さいことを知っています。

BACK INTO ENGLISH

I know that Mads is small.