Advanced custom fields and post types

like people said there is probably a lot of things wrong with your code. so lets start line by line.

whether this is a plugin or a file inside a theme include_once( 'acf.php' ); im assuming you have that file in the same directory as the current file otherwise you are including it wrong.

this define( 'ACF_LITE', true ); needs to happen before it is every define or before it is used/called.

as mentioned before $this in add_action( 'plugins_loaded', array( $this, 'acf_fields' ) ); can’t be called outside a class same goes for &$this it is used to refer back to the class, ‘act_fields’ being your function/method in that class

you really don’t need this add_theme_support( 'post-thumbnails','menyside');
you are already adding the support when you are creating the post type above.