YOU SAID:

we were at the playground things were getting muddy

INTO JAPANESE

私たちは遊び場にいたものが泥だらけになっていた

BACK INTO ENGLISH

What we were in the playground was muddy.

INTO JAPANESE

私たちが遊び場にいたのは泥だらけでした。

BACK INTO ENGLISH

It was muddy that we were in the playground.

INTO JAPANESE

私たちが遊び場にいたのは泥だらけだった。

BACK INTO ENGLISH

It was muddy that we were in the playground.