"We will have created a language."
Translation:Nosotros habremos creado un lenguaje.
I think it would sound weird to say "lengua" in a sentence like this.
No. I've never even heard the word lenguaje before, only lengua, so if anything it's MORE correct
As it turns out, you're right, the word "language" can be translated as "lenguaje" and "lengua", but in Spanish these are two different concepts, "lenguaje" refers to the capacity we have to communicate with each other, while "lengua" is the code that we use to communicate. Therefore a "lenguaje" cannot be created, but a "lengua" can. So this Duo translation is wrong.
Now, the reason I said it sounds weird is because "lengua" can also mean "tongue", so to avoid being ambiguous, I would use "idioma" instead.
Although in English tongue can be used for language. "He speaks a foreign tongue. "
"hecho" was accepted earlier to mean "created" but it is not here. Does anyone know why?
Lengua means tongue which I have heard used to speak of language, like in English we refer to a person's 'native tongue'. But I think in this sentence 'lenguaje' or 'idioma' sounds best.
As native speaker "lengua" or "lenguaje" should be accepted as correct but to refer a lenguage we commonly use the word "idioma".