App from another store?

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There is an app that I'm supposed to be able to get but I think because I've chosen another region, it's unavailable to me. Is there still no solution to Cortana working in one country but with another language? Not everyone living in France for example wants their phone to be in French but if I don't pick an English country, Cortana won't work with English language. I just don't see why it matters what the language is. If I pick France and English as the language, I should be able to run Cortana in English. Does anyone know what the programming issue is here?
Thanks!