I put lies in the grass and it was marked wrong. that would be more common in english.

General question- Does Gras also used for marijuana same as in English?

I thought "the black cat is laying on the grass" would be acceptable

Is "The black cat lies upon the grass." not quite an accurate translation?

"The black cat lies in the grass" is marked as wrong here, but it would be a better translation. The German sentence is also wrong. Human intervention is needed here, to fix what an algorithm can't do.