Need Help with Multilingual Retrieval in Vertex AI Agent Builder

Hi,

I'm building a multilingual chatbot using Creating Data Store, Discovery Engine, and Reasoning Engine.

Right now, I have one data store that contains both English and German documents. The problem is: when I ask something in English, it doesn't retrieve relevant content from the German documents — even if the answer is there.

I'm looking for a solution where the retriever can search across both languages.
For example: if the query is in English, it should also check German documents and return the right response if available.

Any suggestions or best practices would be really helpful!