It's, IME, very common for immigrants (especially those that immigrated in middle age) to be intelligible to native speakers when speaking the local language, but have more trouble understanding native speakers. So one-way translation may be useful.
Really? I have found the exact opposite. You can pick up a lot of clues from words, expression, tone, without knowing the entire sentence. But that doesn't help in talking to them.
(OTOH, it may also mess with code-switching.)