Translate app issues

I have been using the app for a long time, always, every 2 or 3 weeks when I try to translate a word from a language that I had already downloaded before, the app asks me to download it again, not only the language I use but the one I want to translate. As if the app itself deleted those languages but it keeps filling my iPhone's memory. I have had to delete it and download the app but it does the same to me, once I download the languages I want it again asks me to download the same 2 or 3 weeks later