Include Advanced Custom Fields plugin into own plugin

include_acf.php

// Customize path to ACF in own plugin
add_filter('acf/settings/path', 'my_acf_settings_path');

function my_acf_settings_path( $path ) {

	// update path
	$path = plugin_dir_path(__FILE__) . '/pluginname/lib/acf/';

	// return
	return $path;
}

// Customize directory to ACF in own plugin
add_filter('acf/settings/dir', 'my_acf_settings_dir');

function my_acf_settings_dir( $dir ) {

	// update path
	$dir = plugins_url() . '/pluginname/lib/acf/';

	// return
	return $dir;

}

// Do not show ACF in backend of WordPress
add_filter('acf/settings/show_admin', '__return_false');

// Include ACF to own plugin
include_once( plugin_dir_path( __FILE__ ) . 'lib/acf/acf.php' );