"I come to bring her some."
Translation:Je viens pour lui en apporter.
"en" is an adverbial pronoun, that (here) means "some of it" or just "it". Check out this page for more details:
1) The sentence might sound slightly archaic, but it's certainly not wrong. From your translation, it sounds like you do understand it. Unusual phrasing doesn't mean incorrect. It fits in "I come bearing gifts."
2) I don't know the history of why, but we use the present progressive (e.g. "coming") more than simple present (e.g. "come") with the exception of stating general facts: "I'm running on Friday." or "I run on Fridays." However, I find you can usually exchange one for the other: "I'm running on Friday." or "I run on Friday." and the meaning rarely changes much. It's just uncommon.
What if I said, "I'm coming to bring her some."? That one doesn't sound weird.
3) I think the main reason the lesson says it that way is that it's a lot easier to start learning a language if you just stick to one tense. Most of the other Duolingo lessons have been avoiding the present progressive for me (except sometimes German). Try to stay flexible about the present tense. English strays from it more than the other languages I've seen so far (including Old English). Every time I've tried to learn a language, the simple present is overused in English, and I think it's for these reasons.
You need the pronoun before the verb or the à after the verb. "apporter quelque chose à quelqu'un"
The literal is "I come to bring some (of it) to her".
I'm not talking about the direct/indirect object pronouns here. I'm talking about "Verb of motion or intent + infinitive" constructions. I.e. why Duo accepts "Je viens pour lui en apporter." as well as "Je viens lui en apporter." Is "pour" optional where it means "in order to"? As in the expression, "Nous mangeons pour vivre, et nous vivons pour manger." which was mentioned in an earlier lesson and which I missed because I omitted "pour."
Sorry I figured you had meant pour like the person above you. Since apporter is a transitive verb it required direct and/or indirect to complete it's meaning. I don't think it's really "optional" in the sense you mean, but the fact is both sentences have the same approximate meaning.
BTW: level 9 was the annoying point for me, so much more was making sense, but all the exceptions really start to eat away at you.