Ok, between 2 nouns I can understand it very well. However, how should I do it if I have 3 or more nouns?
Example sentence: I’m Yui’s first Portuguese friend.
Translated it as: 私はゆいさんの初めてのポルトガル人の友達です。
Is my sentence correct? If so, is there a special way to order them?
Thanks! (:
なるほど！Well, I asked on HiNative for the translation and a Japanese person actually gave me the one I wrote above. However, yours seems to be logical 
Any special order? Or could I also say 私はゆいさんの友達ポルトガル人初めてです (for example)?
I’ve seen a few examples such as 日本の友達, so I think it’s perfectly correct! One I’ve seen was 私の地理の先生でした。
As far as 初めて, I don’t remember how to use it in a sentence, although both ways seem logical! I’m not quite sure on the difference between using 初めて and 最初 in this context, however. To me, 私はゆいさんの最初のポルトガルの友達です seems perfectly correct.
From Genki. (Hopefully accurate. 
)
Your original sentence
私はゆいさんの初めてのポルトガル人の友達です
is correct.
This is grammatically incorrect:
私はゆいさんのポルトガル人友達初めてです
You are missing particles between ポルトガル人 and 友達. You cannot describe the noun “友達” with “ポルトガル人” to make “Portuguese friend” without the の particle between the two nouns. This might be dropped in casual talk, but you still need to be aware of the particle being dropped. And 初めて is completely in the wrong place.
To say “the first XYZ” you would go 初めての XYZ. So here’s how you can break down your sentence.
I’m Yui’s first Portuguese friend.
I’m Yui’s friend: 私はゆいさんの友達です
I’m Yui’s Portuguese friend: 私はゆいさんのポルトガル人の友達です
I’m Yui’s first Portuguese friend: 私はゆいさんの初めてのポルトガル人の友達です
EDIT:
The Genki snippet by @alexbeldan just above my reply is the important thing to understand. Once you’ve made a noun phrase like 「ポルトガル人の友達」you consider that as just another noun when looking at the larger sentence. So now you have the “noun” for “Portuguese friend”. So to make “first Portuguese friend” you go: 「初めての(ポルトガル人の友達)」. And then finally to complete the thought as “Yui’s first Portuguese friend”: ゆいさんの(初めての(ポルトガル人の友達))です.
EDIT 2:
About 最初 and 初めて, I believe 初めて is more naturally used for the first time people “experience” something as compared to something like “the first shinkansen” where I would tend towards 最初の新幹線 instead. But I am not completely sure about this particular point. Maybe they can be freely interchanged. I’m just going off based on usage that I’ve seen.
Your comment made everything clear! @feanor Thanks a lot for taking the time! ^^ I guess the order of the nouns follows the same logic as in English… I might be wrong 
@UntitledName, I really appreciate you taking the time to help ^^
@alexbeldan Yep, noun + noun I understood very well! But when you add more than that… 
Thank you for saving me the time I was about to spend on this. Great explanation, centered on useful examples.
@MarkGreenway - You have much Japanese grammar to learn.
Since you are just beginning, I’d recommend you practice sentence constructs as you come across them. I don’t mean this as discouragement, but Japanese grammar is not easily mapped to English grammar, so I’d be wary of making strong statements at such an early stage like “I guess the order of the nouns follows the same logic as in English”. That may be true in some cases, but not in others. As you proceed with your Japanese studies, you will learn to recognize them, and understand the underlying Japanese concept itself rather than trying to map it back to English. Asking questions to clarify from a native speaker (as you seem to be doing already) is an excellent way to learn.
would it be ok to say the no nouns works as functions from calculus?
I don’t get why people do this. I see it quite often on Hello Talk - sometimes it’s people “correcting” mistakes with different mistakes, but often it’s people correcting good grammar with bad grammar. I just wonder what’s going through someone’s head when they do that. Especially when they frame it so authoritatively. Weird.
I know what you mean @riccyjay . I think that people are just trying to help out though. They have good intentions. The problem is that most of the times, we think our level in a language is better than it actually is. My native language is Portuguese and I’ve learnt English mainly through using the Internet. Sometimes I feel insecured about correcting some small detail in English because of how I’ve learnt it.
The trick is to double check everything. I’m still grateful for everyone that tried to help ^^
Yep, I’ve been doing that for some time 
I always double check.
Thanks again for the help! Means a lot.
nouns.join('の') + 'です'
Ahh yes… you must be one of my university lecturers. 
This comment is so real it’s almost painful
I hope you’re right.
The part that’s confusing for me is when people do it with such confidence. Maybe this is just me being overly British, but even when I know the answer to something, I usually phrase it as “I think it might be X” or “Would Y be possible here?”. I just don’t know what’s going on when someone sweeps in with a big voice and a bunch of wrong answers.
Anyway, glad you got your answer in the end - like you said, I think double and triple checking everything is the way to go, and never be afraid to reevaluate what you already know if you see something different.
What happened in here? I’m guessing there’s a deleted post or something.
Yes, someone gave an incorrect explanation but later removed their post when it was proven wrong.
How does this work when using a demonstrative like この? I’ve read that この should be the last thing before the noun, but I’m almost convinced I’ve seen it used it other places (though I can’t think of any concrete examples offhand).
Does e.g. 緑のこの車 sound unnatural to me because I’m English-biased (you would say “this green car”, not “green this car”), or is it actually unnatural?
