A translation in multiple parts.

All comments and criticism welcome (I split it into 5 parts, posted in seperate comments) because a wall of text can be somewhat unappealing to read.

Part 1

Original

There was Eru, the One, who in Arda is called Ilúvatar; and he made first the Ainur, the Holy Ones, that were the offspring of his thought, and they were with him before aught else was made. And he spoke to them, propounding to them themes of music; and they sang before him, and he was glad. But for a long while they sang only each alone, or but few together, while the rest hearkened; for each comprehended only that part of the mind of Ilúvatar from which he came, and in the understanding of their brethren they grew but slowly. Yet ever as they listened they came to deeper understanding, and increased in unison and harmony.

Translation

Erat Eru,ūnum,qui in Arda vocātur Ilúvatar.Et Ainur prīmum fēcit,spīritūs beātōs,prōgeniem animī suī,quī cum eō erant antequam aliud quidquam factum est.Et docuit eōs,themata mūsicae eīs dēscrībēns,et cantāvērunt coram eō,et gavīsus est.Sed diū illī cantāvērunt sōlī, aut in parvīs numerīs, dum aliī audīvērunt;prō quisque eōrum partem animī de Ilúvatar, quae eō creāvit intellēxērunt, sed comprehensione fratrum, suōrum lentē crēvērunt.Tamen sapiēntiam profundam dōnāvit,in ūnitātem et harmōniam augent.