About Bilbo's Translating
In this tale, Bilbo is translating an Elvish lay called The Fall of Gil-galad, which is written in 'an ancient tongue' (Aragorn; FotR, p. 251), which I think might be Quenya. Bilbo's translation of this lay appears in the book Fellowship of the Ring (by J. R. R. Tolkien). It is recited there by Sam Gamgee, who learned it from Bilbo when he was 'a lad' (Samwise; FotR, p. 251). Sam recites three verses of Bilbo's translated lay; he says that there was 'a lot more', but that he didn't learn it, because it was 'all about Mordor' and 'gave [him] the shivers' (Sam; FotR, p. 251).
Written out properly, what Bilbo translates in this tale is the following:
Gil-galad was an Elven-king.
Of him the harpers sadly sing:
the last whose realm was fair and free
between the Mountains and the Sea.
He then continues with the first part of the next verse, which I won't put here. There is a third verse as well, but I won't type it out here either. If you want to find it, it's in The Fellowship of the Ring, Book I, Chapter 11 (A Knife in the Dark), on page 250 in my copy (Ballantine edition)...