Muggles' Guide to Harry Potter/Magic/Mermish

Overview
Mermish is the language used by Merpeople.

Extended Description
Heard in air, Mermish is thin and screechy, because Merpeople's vocal equipment is geared to the more viscous aquatic environment. In the thin stuff that is our air, the vibrating bits move far too fast, making the tone of their voices hurtful to human ears.

After the Second Task of the Triwizard Tournament, Professor Dumbledore speaks with the mer-Chieftainess to determine what had happened with Harry and the other Champions under the lake. It is mentioned at that time that Dumbledore knows possibly a thousand languages, including mermish.

Questions

 * 1) In Harry Potter and the Goblet of Fire, how does Harry understand the mermish message within the golden egg?