Let me start with a small explanation:

I am probably a rather rare case of a fanfiction and reader insert lover whose native language is not English and who can understand 5 languages without a problem. And this is the reason why I probably notice things in fanfictions that most others don't. This is why I want to try and make you see what I experience and feel as a reader when I encounter foreign expressions and language in fanfictions.

I hope this entry will help you a little bit if you are unsure if you should use any foreign expressions or not and how I think they should be treated. This, of course, is solely my own opinion, so please keep it in mind. I have absolutely nothing against your own opinions on this topic.  

I really like fanfiction but I especially love Hetalia-related reader inserts because of the foreign languages and the many things I learn while reading them. I think it's pretty awesome that I now can say "I love you" in more than 10 different languages, I know that "ciao bella" is just a way of Italian men to greet a random woman in the street and if someone tells me "brutto porco!" I'll definitely turn around and give that person a hard punch in the face.

And since we are speaking about the use of foreign languages in literature I might as well add this little fact: Foreign expressions are not only common in Hetalia fanfictions, even famous authors use them from times to times. I know at some point the French was very popular among the Russian writers and we can find some French words in German literature as well!  
Of course, when an author decides to use other languages he or she needs to be extra careful, for it is difficult to put the desired sentence or expression in the right place.

Sometimes it may cause more trouble than it's worth in the end.

To make it simple, I would proceed as follows:

Step 1: Ask yourself if it's really necessary to use another language in your fanfiction.
Step 2: If so, ask yourself another question: What do you want to achieve by doing so?


I think it is actually very important to think of the purpose instead of just throwing in a sentence or two because you feel like it might look good. You might want to keep your chosen character "in character" or simply make the character seem more authentic to the reader by occasionally making him say something in his native language. But remember that your reader might not get the meaning if you overdo it or use too exotic words. I would try and use widely known words or make it easy to understand them from the context, like in the following example:
 

Example Nr.1

World Meeting. Our beloved France enters the scene with his famous rose in hand and a wide smile upon his face. Suddenly he spots England and Germany on the other end of the room. Of course, being a sophisticated person, he instantly decides to approach the two gentlemen and greets his neighbours politely.
"Bonjour mes amis," he says happily, "isn't it a wonderful day? C'est très beau!"
"Ja, indeed." Germany replies with a curt nod.

/Explanation:
We all know that France is very proud of his language. (Without a doubt he has every right to feel so strongly about his beautiful language! He is so proud that he prefers to use his language as much as possible, and Germany, as his neighbour, knows very well that it can be quite difficult sometimes. (Just cross the border of France and you will see that he will try to speak solely in French to you.) Of course, since it is a World Meeting and we readers probably don't know much French, France has to use English in order to be understood but due to his character he cannot help but add a few French words here and there. Even Germany slips a little and says "ja" instead of "yes".

These small expressions can be easily understood from the context, they keep our dear France very much in character and make the conversation seem very lovely in my eyes.

Of course, as an author you might want to put in whole sentences in order to achieve other effects.
You might want to confuse the reader because it's important for the plot. For example, your main character suddenly finds him- or herself in a foreign country and does not get a single word! Here I would make sure that the reader can at least read the foreign sentence. After all, there is no point in writing something in Russian when the reader cannot read it and understand how it sounds.

Personally I think it's important to be able to make the reader see and hear the things written in your text. To someone how has no idea how to read something like that: "Россия тебя любит" it's just a weird combination of unknown symbols.

To avoid unnecessary interruptions you can try and describe the said sentence indirectly, this will also save you the trouble of having to use an online translator and probably mess up the sentence if you don't speak the language you want to use.  
I'll give you this example in order to show you want I mean by interruption of the flow.



Example Nr. 2: (reader insert)

After recollecting his thoughts, Iceland is about to say something important. The poor boy looks like he wants to suppress the urge to flee, to hide himself under a mattress and never come out. Then suddenly, he bursts out: "Ég elska þig meira en nokkuð, ég vil að þú giftast mér!"

/ This is what I see in the text. And this is what it looks like to the silly me who does not understand Icelandic: "%hAJH&)-(")§$%!"=?/(&"§%/!&p/(!"&/%/("/e(§--ha8!"

There are three options from here on:

1.
Luckily, I find a footnote or this convenient symbol:"*" which indicates that I can find the translation at the bottom of the page or in the author's description. And because I am a stubborn person, I scroll down in order to find the translation although I would probably rather prefer to read the scene until the end. But, after all, I do want to understand what was said in the sentence! Of course I will find the translation, but if I am not careful enough I might accidentally read the end of the story. That's quite a problem to me because I do not like to spoil the fun for myself. After I found the translation I have to go back; sadly, the mood of the scene is ruined by the small interruption.

2.
I find the translation right after the sentence. Sometimes I ask myself if it is necessary to use the foreign language at all since 1) I cannot read the original sentence anyway and 2) I just read the translation. This might be typical of me, though, and other people might think otherwise.

3.
Sadly, I find no translation. Well, too bad for me!


My suggestion:
This is a reader insert – the reader shall identify himself or herself with the character in the fanfiction. Again, you can try and find a way around the direct use of another language. Something like this sounds nice in my opinion: "His next words were spoken in his native language, they contained such strong emotions and it was evident that they held much importance in them." I'm sure that you can do better than me with my poor writing skills! At least you can definitely be sure that you made no mistakes while translating the desired sentence via online dictionary. In my example, I could not even read the sentence and as a reader I don't have any idea how that sounds anyway.
Just try and think if you really need the sentence and if it's important for the story or not! Less is sometimes more!



Example Nr. 4: Why Google Translate is not always the best option


We all know it, but we still use it anyway.
Yes, we all know that online translators are not an ideal option but there is no way around them in most cases if you do want to use some foreign words. This is actually quite funny if you happen to understand the foreign language as well. Now, most people might not notice that the translated sentence is quite wrong unless when I show you how it is supposed to sound:

Let's say Germany is saying this to Italy: "Italy, you are supposed to work instead of having a siesta!"

What Google Translate tells me: "Italien, soll man arbeiten, anstatt eine Siesta!"

How it sounds if I translate it back to English: „Italy, should one work, instead of a siesta!"

How that sentence should sound in German: „Italien, du sollst arbeiten anstatt eine Siesta zu machen!"

I'll be honest here, Germany sounds as German as my grandma who is Russian and barely speaks any German!

And I cannot help but put another small opinion of mine: What I often see is that many, many expressions, for example in Russian, do not fit into the sentence at all. It sounds weird, combined with the English. I think that sometimes a simple "my sunflower, you are my most important treasure" sounds better than an experiment with mixing the Russian expression with the English one. It may just be me because I can read both things and in the end the sound is not that nice than it could be.


That aside, I think it's totally okay if your grammar is not perfect, my English is not that perfect, either. But maybe you should just try and find someone who looks over your sentence if you need to use it in your fanfiction. I understand that it might not be easy to find someone who understands Icelandic but I would at least try.
After all, you could see it as a part of a learning process!
Everybody can use Google Translate but not everybody has the strength to research well and try and find the best solution. There are sites where you can post questions, too. It may take a while, but at least in the end you can be especially proud of your result.

Now, the last thing I would like to mention is something which depends on you:

The correct spelling of foreign words.

This should not be a problem if you use a decent translator and copy and paste the words into your text. But, for some reason, I sometimes see the same mistakes here and there. If you do decide to use the words, then don't forget to add the correct accents! Be careful with Spanish and French words and don't forget that in German the nouns are written with capital letters. If you are careful and copy and paste from the online dictionary then it should be okay. It's really not difficult at all



And finally, as a German-speaking country, Prussia would like to give you some awesome advice on frequently used German words and expressions that some people tend to spell wrong:
NOW LISTEN TO THE AWESOME ME!

"I love you." – "Ich liebe dich." (take notice that you write it with "ie", as well as the word "love"-"Liebe", be awesome and don't swap the "i" and "e", otherwise your result might sound quite weird!)
"my woman" – "meine Frau" (note that you write it with an "e" because the word "woman" has a female gender) Prussia would also like to add: "This expression usually refers to a married woman, it's the same as if you would say 'my wife'. So be careful because it sounds very possessive!"

Of course, being the awesome me, I cannot help but suggest the following expression:
"Süße" - "cutie", although the awesome me thinks that your favourite expression suits me well!
You can always ask the awesome me if you are unsure about your German sentences or expressions, the awesome me will gladly help! But now I have to take care of Gilbird, so please excuse my awesomness!


Now, you may ask yourself: 'Why should I care?' especially because most people would not notice the difference anyway.
It's actually very simple:
I assume, no, actually I am sure that as a Hetalia lover you respect other countries and cultures, right? If that is the case then surely you respect their languages as well. It would make people like me very happy. I like it when someone uses German in a fanfiction including Germany and actually cares enough to spell the words in a correct way.
Also, a fanfiction is also a piece of art and, just like a precious painting, it should be treated as such. I would try to make it as perfect as possible before posting it and showing it off to the world. Mistakes and wrong grammar are totally okay, hey, we're all humans, after all, but that doesn't mean that we cannot at least try. We are all lazy and I know that sometimes an author has the urge to post his or her fanfiction as fast as possible. But never forget that your readers will appreciate it when you try and give your best!
Thank you for reading this,
Have a good day!