Translation:The small elephant does not eat well.
"Well" is an adverb and so describes a verb; "good" is an adjective and so describes a noun. Since the sentence is describing how the elephant eats, it should be "well". Even many native English speakers use "well" and "good" incorrectly, but that is the correct usage.
It still makes little sense. These sentences should be every-day, commonly applicable. Some of them are just nonsense.