The official import/export program for the Bilingual Shopify Theme is GOOGLE SHEETS (Google Docs).
We have heard about corrupted characters in various forms, and talked with Shopify's helpdesk about it. The summary is: Microsoft Products like Excel can corrupt foreign characters when importing into Shopify. Use Google Google Sheets to edit all csv files. If you notice corrupted characters in your Excel file when you export from Shopify, don't import it back in, or your characters will be corrupted after the import too. This is a Microsoft problem related to MS Excel, not related to Shopify or the bilingual theme. The problem is that, sometimes, MS Excel opens the file however it feels like, without respecting the characters inside. Some suggestions below.
Important disclaimer: With so many operating systems, computer models, and versions of MS Office and other programs, we can't guarantee that the below fixes will work in your situation. If in doubt, make multiple backup copies, and/or contact Shopify or your software provider, like Microsoft, if you can't get it working after trying the options below. These are provided on a best-effort basis, as-is.
Option 1: In Shopify, go to Admin > Export Products > Export All Products. Download the file but *do not open it*. Opening it will just corrupt the characters again. What we need to do is import it into Google Docs, which is better than MS Excel at preserving the characters.
Next, open up Google Docs and go to Import > Spreadsheet. This is how I have had the most success in seeing & working with alternate character sets. Make your updates, then export back to CSV but don't open it. Try important ONE TEST PRODUCT ONLY back into Shopify, to see if your characters work after exporting from Google Docs. If they do, you *should* be ok to import back into Shopify. Check it first!
Option 2: If you have the software called "Numbers", which is Mac's version of MS Excel, this is supposed to handle characters better and work smoothly. I have heard people having better success with Numbers than with Excel.
Option 3: If none of those work, you may need to update your products manually or try looking for another solution. We'll update this FAQ section if and when we find solutions.