This seems to me more a Kodi problem than a LibreELEC problem. Translations for Kodi are done via the Transifex online tool. You can help translate Kodi into Hindi. You can register for free.
You need to add a font that supports Hindi characters to /storage/.kodi/media/Fonts/ and reboot. If there is no translation for a string (which is likely if the content is only 18% complete) you should see English characters in the GUI.