Oooh how fun! How hard can Danish be if you speak Dutch and German?
Hm... "det hedder Gil-galads fald"
Well, the latter part is obviously "The Fall of Gil-Galad."
"det hedder" is then probably "dat heet" or "das heisst" in German, which would make it say something like "It is named / called the Fall of Gil-Galad."
"det er digtet pĺ et gammelt sprog Bilbo mĺ have oversat det."
Uh, that's a bit harder. I may be completely off here. "gammelt" sounds like the Dutch word "gammel" which has something to do with being old and broken. So it might mean simply old. "sprog", considering that this is Tolkien we're talking about, may very well be the Dutch word "spraak" and the German word "Sprache" which would translate to language or tongue in English. So gammelt sprog is ancient language.
Oversat sounds remotely like ubersetzen... which means translating. I think Bilbo did that sometimes.
The last part is too hard. "Vidste" might be "wisten". Which means knew.
I don't know the books quite well enough, so I'll leave the rest to someone else I suppose. That is, if my translation is even remotely correct.
Edit: ai Nilp, you cheater. I was trying it the hard way.