Have you ever tried talking to somebody in another language that is not your own? Have you ever tried using Google translate and was unable to convey the message across that you wanted to convey?
When writing fantasy or science fiction, don't expect the languages to all sound like English. That's lazy and eurocentric. If you look at Tolkien and others, they created new and interesting languages, and that's amazing. Now the purpose of this post is not to tell you how to create a new language, because I don't know how to do that. What I can tell you though, is how communication between languages is not as easy as it should be in fiction, and also ways in which it CAN be easy.
I once read a science fiction series where humans separated for thousands of years could still understand each other. If you look at today, new slang is always popping up with the next generation. "Cool" was the new "rad". "Lit" is the new "cool". But I'm also not here to write about how you have to be up to date on all the latest slang. As long as you write dialogue that makes sense to the common reader, across all ages, people will line up in droves to buy your book.
I'm focusing mainly on communication in science fiction, because that's what I'm currently writing. For a bit of background, I speak Mandarin Chinese, English, a little bit of Spanish, and a little bit of Burmese. I can tell you this: when I speak Chinese my relatives and community who speak way better than me sometimes laugh (with me). It's as simple as saying "carpenter" vs. "wood working man". The first sounds professional, and the second is laughable.
If you want some realism in you writing, take a look at the world around you. There are dozens or hundreds of Chinese dialects. Cantonese is not the same as Mandarin. If you look at the English language, there are differences between British, Australian, and US accents. Even the United States has different accents! So put some of that realism into your writing!
You will make you writing more humorous if you can inject some "lost in translation" dialogue into your book. I went to Google Translate, and I typed in "we come in peace". That's something we usually associate with aliens visiting Earth for the first time. I got the results for the translation in Chinese, and it came out like 我們安息吧. Don't worry about not being able to understand that part for now. What I did next, was I copied and pasted the Chinese words back into the translator, re-translating it back into English, and I got "Let's rest in peace". Totally different meaning, right?
This is realistic, but it doesn't necessarily always need to be this realistic. I'll explain why later. For now, just know that this is how translation works with modern technology. If aliens had the technology to visit Earth they should definitely be using translators! This isn't the 17th century!
Back to the sample translation of "we come in peace". This is an English phrase. The words do not have the same context in another language. The translator translated "peace" as "rest in peace". Google Translate is funny to the translating community because you almost always get strange translations.
Now that I've covered why it's realistic to include some funny "lost in translation" moments in science fiction, I'm going to cover why it isn't always practical to do so. Ultimately you have to find that balance yourself, because too much of this can slow the book down. But if you can do it right, you can raise the tension/stakes of your writing.
Translators are capable of machine learning. Technology nowadays is getting better at translating right away. It's not hard to assume that technology of the future, at least on Earth, can translate something perfectly.
Now translate (haha, get it?) that into alien technology. If aliens had spaceships that could reach Earth, don't you think they would have some way to absorb vast amounts of information? All the languages on Earth and all our accents - they'd be able to absorb all of that right away and their machines would quickly learn how to translate that automatically. However, not all Earth languages are catalogued. Some dialects are not in the records because they don't have internet access or because their dialects and customs are passed on through oral traditions, not uploaded to the internet. There is also a lot of false information out there and self-proclaimed experts on language and other things. Alien machines trying to sift through all that information are bound to come upon some problems.
I'm writing military science fiction now. I have plans to write a fantasy series one day centered on a flat world. Imagine what would happen if there was miscommunication in a fight? Would people die? Would entire worlds fall?
Regarding raising the stakes, if done in a limited fashion, words lost in translation can help the reader feel sympathy for people who die due to this. Readers empathize with something that happens, that they just wish didn't happen. It was out of their control and victory was so close, but it was botched due to a small mistake. This is something everyone can empathize with and can bring some drama to your story, as long as it's all in moderation.
If you're writing fantasy, then trying to create a language from nothing is pretty difficult. You're better off creating just a few simple words, then writing "he said in (insert fantasy language)".
So to conclude, don't be afraid to learn a new language. It can help you with writing science fiction miscommunication because you will understand how difficult it is. If you can't learn another language for some reason, that isn't an issue either. As long as Google Translate continues to be imperfect, we writers can use it to make our writing funny and realistic. Just paste the words you want to translate, get that translation, then retranslate it and use that new translation.
I've got to get back to the writing now. I'm writing my first scene with dozens of alien spaceships appearing in space with blink drives.