Translate for a single language
The SEA theme is set with the English default. But it is easy to translate into another language. We suggest you install the free Loco Translate plugin. Please read the article.
Website with Multi-language
There are 2 solutions to make the multi-language WordPress website. The WPML is a popular plugin, it is not free. The Polylang is a free plugin, but there is not the page duplication function.