We actually translate culture not language because language is a product of culture. Language is medium to translate culture. Though, psychologically linguistic sounds influence human propensity and at the same time culture is abstract but it is this abstract we are seeking always to translate that is the problem of the translation. For example in English and French, the way English man thinks is different from the way French man thinks because of the influence of culture on language vice versa.
Language is a uniquely human gift. When we study language, we are uncovering in part what makes us human, getting a peek at the very nature of human nature. As we uncover how languages and their speakers differ from one another, we discover that human natures too can differ dramatically, depending on the languages we speak. The next steps are to understand the mechanisms through which languages help us construct the incredibly complex knowledge systems we have. Understanding how knowledge is built will allow us to create ideas that go beyond the currently thinkable. There is a unique tie between culture and language. The languages we speak provide us with the words and concepts to describe the world around us, allowing us to verbalize certain values easily. Anything we as a cultural group value will surely have a known and easily understandable term. Languages also have differing structures that can reinforce and contribute to our worldview and cultural beliefs. Take, for example, languages such as Spanish that quickly and easily differentiate between a “formal” and “informal” relationship with others, depending on which form of the word “you” is used. In learning this language as a child, you are taught that an appropriate way to demonstrate respect to certain other people is in word choice… and because this is part of how you must speak, it becomes part of how you must think. Languages, of course, are human creations, tools we invent and hone to suit our needs. Simply showing that speakers of different languages think differently doesn't tell us whether it's language that shapes thought or the other way around. To demonstrate the causal role of language, what's needed are studies that directly manipulate language and look for effects in cognition. Take "Humpty Dumpty sat on a..." Even this snippet of a nursery rhyme reveals how much languages can differ from one another. In English, we have to mark the verb for tense; in this case, we say "sat" rather than "sit." In Indonesian you need not (in fact, you can't) change the verb to mark tense.
I wonder if you could clarify or explain what you have in mind with your phrase, "cultural expressions." In one sense, it seems that any expression might count as a "cultural expression," but I suspect that you may have in mind expressions or meanings specific to particular cultures. How are they to be translated?
Again, I suspect that you might help by explaining the difference between "a language's culture" and "the cultural language." Might you illustrate the distinction you have in mind?