Adding rich text editor to my plugin

Hello WordPress users,

I’m trying to add a rich text editor to my own plugin.
So I googled it first of course and I found serveral answers like:
https://www.dev4press.com/2010/tutorials/wordpress/tips/add-rich-text-editor-to-your-plugin/
https://stackoverflow.com/questions/10377496/add-rich-text-editor-in-wp-plugin

This code displays nothing so I tried finding a another solution:

https://www.ads-software.com/support/topic/adding-rich-text-editing-to-your-plugin?replies=15

This displays a rich text edtior like :
https://oi35.tinypic.com/mwcsug.jpg

This seems to work fine, but as soon I switch to the WYSIWYG tab the text I inserted is deleted, I only see a blanco field and I can’t type anything.

Is someone familiair with this problem?
Is this a bug or what can I do to make it work?

FYI these scripts and styles are included in my plugin:

function highlights_style() {
    wp_enqueue_style('thickbox');
}

function highlights_script() {
    wp_register_script( 'jquery.js', HIGHLIGHTS_PLUGIN_URL . 'jquery.js', array('jquery','media-upload','thickbox'));
    wp_enqueue_script( 'jquery.js' );

    wp_enqueue_script('media-upload');
    wp_enqueue_script('thickbox');
    wp_enqueue_script( 'editor' );

    wp_enqueue_media();

    add_action( 'admin_head', 'wp_tiny_mce' );
}

And I use this to display the editor:
the_editor( '' , 'content' );

I hope someone can help me!
Thanks!