i use the function below to show content under the_content. It works on pages which uses template-test.php. But on other pages the_content stops output.
function beschreibung_kriterien( $content ) {
if ( is_page_template( 'template-test.php' ) ) {
$content .= '<h2>Test</h2>';
return $content;
}
}
add_filter( 'the_content', 'beschreibung_kriterien', 5 );