How do I create a multi-language online store?

You can complete the task by placing different versions of the catalog in different websites: each one for its own language version. To do this, you need to switch to the Business plan that allows you to create up to five websites included: https://tilda.cc/pricing-compare/. You can buy the Business plan in the Plans and Billing tab.

In one project, you should connect your domain. In the domain registrar's panel, you can create a subdomain for it that can be connected to another project in Tilda using this guide as well: https://help.tilda.cc/customdomain. By doing so, you can create a multi-language Catalog.

Detailed guide: https://help.tilda.cc/online-store 

If you need to add more languages in the menu, you can use this guide: https://help.tilda.cc/menu#two-levels