Line from the Lay of Beowulf

To the Reader,

I sincerely apologize for the poor quality of this translation. I am just beginning in studying Elvish and still do not have a great grasp of the grammar. However, I have found in learning other languages that I learn best from reading and writing translations. So below I have translated two lines from Tolkien's Lay of Beowulf into primarily Sindarin (names are in Quenya). Please comment on my mistakes and tell me where there should be correction. I will admit I currently have no working understanding of lenition and consonant mutation, so there may be many mistakes in this regard. Thank you for reading!

Harmanion maethant ah Grendelon ennas,

a rancdeid a gampdeid marchannir o

It would have been better if you shared what you are trying to translate, because it is impossible to understand even what it is supposed to mean. For now I can say that Sindarin does not allow consonant clusters like "NCD (rancdeid)" and "MPD (gampdeid)", nor final "EI (deid)" (unless archaic). Then the seemingly random variance of "a & ah", without mutation, but we have more pressing issues. And a preposition that precedes nothing (that last "o"). More to say, but like I said, there are more important problems for now.