If you want to translate your site from English language to another language, then please install that language first.
Site administration settings:
Administrators can install other languages from Site administration > Language >Language packs and then view or modify the default language settings from Site administration > Language > Language settings.
Force the site language:
By default, Moodle detects a user’s language from their browser setting. If you as admin want to force the default site language instead, you can disable this from Site administration > Language > Language settings > Language autodetect.
Default language:
From Site administration > Language > Language settings > you as admin the default site language and then any accounts you create will use this language, unless you specify a different one.
Changing this default does not change the default language of already existing users. See the FAQ ‘When I change to a new default language, users still have the old language.’ in Language FAQ for workarounds.
The priority of language selection from site to course to user can be seen in this graphic: Language selection priority
You can enable localised error messages for database connection problems by add the following line to your config.php file:
$CFG->lang="yourlangcode";
If you don’t want the language menu to display, then turn it off from Site administration > Language > Language settings. Note that the language menu displays differently according to the site theme. In the Boost theme, it appears in the top bar on the upper left of the screen, to the right of any theme custom menu items.
After switching the site language, you can translate site all content into your language from Course/Page or other pages/blocks