Read the excerpt from The Riddle of the Rosetta Stone, by James Cross Giblin.

De Sacy, Akerblad, Young, Champollion, and others all made some progress in translating the demotic passage. But the first scholar who fully understood the symbols in the demotic text was a German, Heinrich Karl Brugsch, who published a translation of it, with commentary, in 1850. An even more thorough version was published by another German scholar, Dr. J. J. Hess, in 1902.

The details from the excerpt best support the idea that

Champollion was the most well-known scholar to work on the Rosetta Stone translation.
translating the demotic text on the Rosetta Stone took the work of many scholars.
the demotic text on the Rosetta Stone would still be a mystery without the work of Dr. J. J. Hess.
the best translation of the demotic text on the Rosetta Stone was in German.