Preserve Language context in Plugin

Within a plugin, i want to use translations from the site.yml blueprint (The page is multi-lang, so the site blueprint has a and a site.en.txt file.

In a src class from a plugin, i want to use the following:

$destination_email_address = (string) site()->transfer_destination_email_address();

Since this is a plugin, site() seems to return the default language strings, not translated ones. How can i change the context or make the site() return the english version of the field?

that takes a language param.

…And how i can get ->transfer_destination_email_address() from there? Using it on $page->content(‘de’) doesn’t work…

Okay, actually it worked this way:
$destination_email_subject = (string) kirby()->site()->content($lang_iso)->transfer_destination_email_subject();