YOU SAID:

there is black stuff beneath my fingernail

INTO JAPANESE

私の指の爪の下に黒いものがあります。

BACK INTO ENGLISH

That black stuff under my finger nails.

INTO JAPANESE

私の指の爪の下で黒いもの。

BACK INTO ENGLISH

Under the fingernails of my black ones.

INTO JAPANESE

私の黒いものの好評。

BACK INTO ENGLISH

The popularity of my black ones.

INTO JAPANESE

私の黒い物の人気。

BACK INTO ENGLISH

The popularity of my black ones.