Christian Speculative Fiction discussion

I'm two weeks away from starting my next novel, I still haven't come to a concrete idea of how I'm going to handle this, and any feedback or ideas would be lovely!

So here's what's going on:

This novel I'm about to start writing is the sequel to one of my previous novels. In that first novel, the humans and the goblin-like creatures spoke different languages. They generally didn't care to learn each others' languages very well, so the goblins spoke the human language haltingly, and with unusual grammar conventions because they were so used to their own language's very different syntax. Even the goblin character who had the best command of the human language still spoke it in the goblin syntax.

Later in the book, one of the human characters gained the ability to understand the goblin language. In the chapters written from his POV, when the goblins spoke their language, I wrote it in English but put it in italics to indicate it was a different language. In their own language, of course, the goblins had perfect grammar and were very articulate.

The sequel takes place six years after the first book. I imagine in that time span, the human main characters have devoted time to learning the goblin language. It's implied that the goblin language is very difficult for humans to learn and speak, but these characters are close friends with the previously-mentioned goblin character and they've spent a lot of time together. So I think it's not a stretch that in six years the humans could become conversational in goblin, and understand the goblins to the point where I could write goblin language as grammatically correct English from the humans' POV.

Although this story will mainly focus on the goblins, the human characters still use the human languages with other humans. But I'm not sure how I feel about continuing to use italics for the goblin language, since it's actually going to be more prominent than the human languages. I'm considering switching things around and using italics for the human languages. But I'm wondering how much sense that would make when the story will be told entirely from the POV of a human character whose first language is one of the human languages. If I keep using italics for the goblin language, though, I'm not sure how good it would look to a reader to have entire chapters where all of the dialogue is in italics because everybody's speaking goblin.

An alternative would be to have the goblin main characters speak human most of the time, but that wouldn't sense when, as I mentioned, most of the plot takes place in goblin-populated areas where the humans are the odd ones out. And I think it would also do a disservice to this goblin character who is very intelligent and well-spoken in her own language, but sounds rather silly when she speaks human. Maybe it was part of her charm in the first book, but I'm feeling ready to move on from that idea. Plus, one of the other main characters in this sequel is a goblin who has not spent much time around humans, and I'm not sure he would know anything but a few basic words in the human language.

Right now I am leaning toward putting the human language in italics and rendering the goblin language as un-italicized, normal English, even though, like I mentioned, it seems a bit counterintuitive for a POV character who is not a native goblin-speaker. But I'd like to get some other thoughts on the matter before I commit to anything.

Bilingualism is REALLY hard to tackle. I have some different languages in some of my WIPs as well---Elvish and Dwarvish, mainly. The way I've seen it handled the most adeptly is to simply say in the narrative that "Jimmy switched to Goblin" and then continue writing in English. Or something like that! This way you can omit italics completely.
UNLESS you're writing from the POV of a non-Goblin speaker. If that's the case. throw in some Goblin words as humans hear them, like "traflgrk omnidorb" or something. That adds some depth to the world-building without being too obnoxious. And whatever you do, don't tell the reader what Goblin sounds like (like a snarling cat or a clearing throat), or make the characters tell them!! Let the readers figure out how it sounds through how the letters on the page look. That, I think, is a little more interpretive.
Hope this helps somewhat!

Thank you for your insights! Yes, I don't know what I was thinking when I introduced such a complex language situation into this fantasy world. I like to challenge myself with my writing, but sometimes I bite off more than I can chew.

I hadn't thought of just noting in the prose that a character is switching languages. I will have to try that and see if it happens too often that it starts bogging down the prose. Some elements of life are just so difficult to translate properly into the written word!