Put teaser content, more-link and full content in different divs if existing… Possible?

Found a solution which is working.
Splitting the array like above just gives you the plain text so shortcodes wont work.

this works:

global $post;
$content = get_extended( $post->post_content ); //get the_content

$excerpt = $content['main']; //get the teaser part before more tag
$main_content = apply_filters('the_content', $content['extended']); //get part after more tag

echo $excerpt; //post teaser part
echo $main_content; //post main part

my head is smoking. too much for a beginner

and if you want to have

in your html use this:

echo wpautop( $main_content );