To get a better experience during search it’s recommended to enable what are the languages you plan to use in Zylon for content (Chats, documents, Agent Flows), the default language is english but multiple languages can be enabled. 
languages:
  keywordSearch: ['en', 'es', 'de']
The list of available languages is the following:
LanguageISO 639-1 Code
Arabicar
Armenianhy
Basqueeu
Catalanca
Danishda
Dutchnl
Englishen
Finnishfi
Frenchfr
Germande
Greekel
Hindihi
Hungarianhu
Indonesianid
Irishga
Italianit
Lithuanianlt
Nepaline
Norwegianno
Portuguesept
Romanianro
Russianru
Serbiansr
Spanishes
Swedishsv
Tamilta
Turkishtr
Yiddishyi
Check if your desired language is supported by ISO-639-1.
You can enable/disable languages in any moment, just change the configuration and restart Zylon