Furthermore, there is no such thing as a "concept that cannot be expressed" in a language. More often than not when people say a language has "no word for X", they turn out to be wrong, and even when they're right, the concept can be expressed through paraphrase.
That's why we have loanwords.
Why else would a bouquet not be called "a bunch of flowers". Because a bunch of flowers is something different than a bouquet.
The response to the parent comment was more to debate that there are a lot of words, concepts, and idioms that may carry an actual translation or similar concept in another, but the translations fail to capture the immediacy of the idea conveyed by the original word or phrase. It's not to say that there is no way to understand or interpret these bits of language unless you're a native speaker, it's that in many cases you lose a lot of the meaning without the cultural context surrounding it.
Culture and language are pretty inseparable; it's why transliteration is often frowned upon when doing translation works, and localization is considered important to helping the audience understand without imparting too high of a burden of knowledge of their part. Sometimes this burden of knowledge is simply unavoidable. But the ability of a word or phrase to evoke a specific idea/image/feeling in one language and to not do so in another is not impossible. If you know anyone for whom English is a second language (and has not spent extended time in the US), try to explain why "cut the cheese" is funny in English. They may understand conceptually that there is a rude meaning to the phrase, but I'm willing to bet they'd be more than happy to tell you that they'll cut the cheese in the kitchen.
The same way most languages have singular and plural, Slovenian also has dual. It's much handier than always specifying "two somethings". Very few languages still have this feature. English for instance only has residual traces left.
https://en.m.wikipedia.org/wiki/Dual_(grammatical_number)
You can translate it, of course, but it's going to look and feel awkward.
Have you made a serious effort to translate jokes, poetry, or advertising slogans between unrelated languages before you made that assertion? Were your clients unequivocally satisfied with your work?