plugin shortcode not working on ajax request call

…ajax calls can’t show shortcodes because of the admin ajax url that they dont have full access to wordpress enviorment

Not true. AJAX calls have exactly the same resources at their disposal as regular WordPress requests. Just make sure to parse the content in the same way the_content() does:

$parsed_content = apply_filters( 'the_content', $post->post_content );

Update: Your code is a mess, try this instead:

function prefix_load_proyect() {
    if ( ! isset( $_POST['proyect'] ) || ! $post_id = absint( $_POST['proyect'] ) )
        return;

    if ( ! $post = get_post( $post_id ) )
        return;

    echo apply_filters( 'the_content', $post->post_content );
    exit;
}