I have added custome page '/member-logout/' in nav walker for user logout.
When activated then the function 'render-logout' is fired

    function render_logout() {
		if ( is_user_logged_in() ){
             wp_logout();
		} else {
            echo "You are not logged-in">'; 
        }
    }

the logout works but generates a lot of warnigns of 

Warning: Cannot modify header information - headers already sent by (output started at /home/........./formatting.php:5081) in /home/s..../wp-includes/pluggable.php on line 915 

and redirect after logout does not work

    	public function redirect_after_logout() {
		$redirect_url = home_url( 'member-login' );
		wp_redirect( $redirect_url );
		exit;
	}
    add_action( 'wp_logout', 'redirect_after_logout' );

The link below works very well but this is not loaded automaticly.

    <a href="<?php echo wp_logout_url( home_url() ); ?>" title="Logout">Logout</a>

Any idea how to run this link using wp_redirect or something similar?