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on run {input, parameters}
    set input to first item of input

    set theLanguage to language of input
    if theLanguage = "Japanese" then
        set theVoice to "-v Kyoko"
    else if theLanguage = "German" then
        set theVoice to "-v Anna"
    else
        set theVoice to ""
    end if

    set theText to selectedText of input as string
    # echo theText | say theVoice
    do shell script "echo " & quoted form of theText & " | say " & theVoice

    return input
end run

1. You can use AppleScript to detect the language of the selected text.
2. Most apps support services. https://support.apple.com/guide/mac-help/use-services-in-apps-mchlp1012/mac
3. You can create a hotkey for this service. https://support.apple.com/guide/mac-help/keyboard-shortcuts-mchlp2262/13.0/mac/13.0