Translation:The black cat is lying on the grass.
I put lies in the grass and it was marked wrong. that would be more common in english.
I think it concern of the height of the grass. For 2 inch high grass I am for "auf", while for 10 inch high grass "in" works well.
"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.