Multilingual search on the website

Hello, I am interested in making a multilingual search on my website.

This is a job board, and when I am trying to search on Russian language site find nothing, the opposite thing with listings on the English language. Is there a mistake in listings and search connection or do I just need to add one more language option to the search setting or something like this?

The URL is:
Thank you in advance.

Best Regards,

Here is my site Read-Only: LINK
(how to share your site Read-Only link)