Add this code into header.php of your child theme.

Please make all changes to the child theme files, and do not add the code directly to the theme files, otherwise after updating the theme your fixes will be lost

header.php

// Groovy Menu integration code
if ( function_exists( 'groovy_menu' ) ) {
	groovy_menu();
}

Alternative method

header.php

<?php
/**
 * The header for our theme
 *
 * This is the template that displays all of the <head> section and everything up until <div id="content">
 *
 * @link https://developer.wordpress.org/themes/basics/template-files/#template-partials
 *
 * @package Airi
 */

?>
<!doctype html>
<html <?php language_attributes(); ?>>
<head>
	<meta charset="<?php bloginfo( 'charset' ); ?>">
	<meta name="viewport" content="width=device-width, initial-scale=1">
	<link rel="profile" href="http://gmpg.org/xfn/11">

	<?php wp_head(); ?>
</head>

<body <?php body_class(); ?>>
<div id="page" class="site">
	<?php if ( function_exists( 'groovy_menu' ) ) { groovy_menu(); } ?>
	
	<a class="skip-link screen-reader-text" href="#content"><?php esc_html_e( 'Skip to content', 'airi' ); ?></a>
	
	<?php if ( ! function_exists( 'groovy_menu' ) ) { ?>
		<?php $menu_layout = airi_menu_layout(); ?>
		<?php get_template_part( 'template-parts/menus/menu', $menu_layout['type'] ); ?>
	<?php  } ?>

	<div id="content" class="site-content">

	<?php
		if ( !is_page_template( 'page-templates/template_page-builder.php') ) {
			echo '<div class="container">';
			echo 	'<div class="row">';
		}
	?>
Note: You can find the child theme for the Airi Theme in the Groovy Menu > Integration section