switch language in general text

Currently only the titles are changed on the onepage site based on the language selector, however not the descripion of the page. It would be great if the description could be shown in the language that is selected.

I tried the following in the 'source' of the [description] field, but it is not working properly (language is not changing):

<div id="content">
    <p style="display:block;" lang="nl">
        WELKOM!
    </p>
    <p style="display:none;" lang="de">
        WILLKOMMEN!
    </p>
    <p style="display:none;" lang="en">
        WELCOME!
    </p>
</div>