How to change default language of wordpress website with loco translate plugin?

I have wordpress website with loco translate and two languages russian and ukrainian. First russian language was created and later added ukrainian, therefore russian language loading by default when you visit the page. I want the main page to load in Ukrainian by default. That is, main.com/index.php is the Russian version, but you need to change it to main.com/uk/main-ua

What i tryied ? I did a redirect, but then the Ukrainian version is always loaded and it is impossible to change the language. In the site settings, I set the default site language to Ukrainian, but this had no effect, as it was loaded in Russian and loaded. I put in wp_config line define('WP_HOME', 'main.com/uk/main-ua') but it has no effect, russian version main.com/index.php is loaded anyway. In the database, in the table wp_options, i changed the corresponding settings, the links in the menu changed to the "ukr" version, but the text of the links was not there, and the content of the main page remained "russians". I'm confused now how to did it correctly. Who did this, give advice. Thanks.

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