Hi there,
In what language are you trying to use the theme?
The theme will display in whatever language is set for your site itself at Settings ->General in the dashboard, provided the theme itself has been translated into your language, of course.
You can find the translation project for Resonar at https://translate.www.ads-software.com/projects/wp-themes/resonar/
That said, please keep in mind this theme hasn’t been updated since 2017, and it doesn’t support either the block editor or the site editor introduced in WP 5.9, so personally I’d recommend you look for a newer theme instead ??
