Cómo integrar Google Analytics G4 en el header de mi tienda Prestashop sin causar errores

Buenos días. ¿Alguien sabe cómo puedo meter el siguiente código de Analytics G4 en el header.tpl de mi tienda prestashop sin que se rompa?

<!-- Global site tag (gtag.js) - Google Analytics -->
<script async src="https://www.googletagmanager.com/gtag/js?id=G-KSLYYLYCC1"></script>
<script>
window.dataLayer = window.dataLayer || [];
function gtag(){dataLayer.push(arguments);}
gtag('js', new Date());

gtag('config', 'G-KSLYYLYCC1');
</script>

EL código fuente del header.tpl es este:

{*
Version: V1.0.2
Modificated: 2019-09-05
Author: xxxxx
*}
{block name='head_charset'}
<meta charset="utf-8">
{/block}

{block name='head_ie_compatibility'}
<meta http-equiv="x-ua-compatible" content="ie=8">
{/block}

{block name='head_seo'}
<title>{block name='head_seo_title'}{$page.meta.title}{/block}</title>
<meta name="description" content="{block name='head_seo_description'}{$page.meta.description}{/block}">
<meta name="keywords" content="{block name='head_seo_keywords'}{$page.meta.keywords}{/block}">
<meta name="robots" content="{$page.meta.robots}">
{if $page.page_name ="product"}
{assign var=img_social_share value=$product.cover.bySize.large_default.url}
<meta property="og:image" content={$img_social_share} />
{/if}

{if $page.canonical}
<link rel="canonical" href="{$page.canonical}">
{/if}
{/block}

{block name='head_hreflang'}
{assign "alternative_langs" $urls.alternative_langs|default:[]}
{foreach $alternative_langs as $code => $pageUrl}
<link rel="alternate" href="{$pageUrl}" hreflang="{$code}">
{/foreach}
{/block}

{block name='head_viewport'}
<meta name="viewport" content="width=device-width, initial-scale=1">
{/block}

{block name='head_icons'}
<link rel="icon" type="image/vnd.microsoft.icon" href="{$shop.favicon}?{$shop.favicon_update_time}">
<link rel="shortcut icon" type="image/x-icon" href="{$shop.favicon}?{$shop.favicon_update_time}">
{/block}

{if $page.page_name == 'index' && $djv_flags.template.opinions.trustivity}
<link href='//www.trustivity.es/css/style_widget_trustivity.css'
rel='stylesheet' type='text/css'>
{/if}

<link href="https://fonts.googleapis.com/css?family=Open+Sans:300,400,600,700,800&display=swap" rel="stylesheet">
<!--link
rel="stylesheet"
href="https://stackpath.bootstrapcdn.com/bootstrap/4.1.3/css/bootstrap.min.css"
integrity="sha384-MCw98/SFnGE8fJT3GXwEOngsV7Zt27NXFoaoApmYm81iuXoPkFOJwJ8ERdknLPMO"
crossorigin="anonymous"-->
{block name='stylesheets'}
{include file="_partials/stylesheets.tpl" stylesheets=$stylesheets}
{/block}

{block name='javascript_head'}
<script>var djv_project = '{$djv_project}'; </script>
<script src="https://ajax.googleapis.com/ajax/libs/jquery/3.3.1/jquery.min.js"></script>
<!-- Latest compiled JavaScript -->
{if $djv_flags.template.gtm.id}
<!-- Google Tag Manager -->
<script>(function(w,d,s,l,i){ w[l]=w[l]||[];w[l].push({ 'gtm.start':
new Date().getTime(),event:'gtm.js'});var f=d.getElementsByTagName(s)[0],
j=d.createElement(s),dl=l!='dataLayer'?'&l='+l:'';j.async=true;j.src=
'https://www.googletagmanager.com/gtm.js?id='+i+dl;f.parentNode.insertBefore(j,f);
})(window,document,'script','dataLayer','{$djv_flags.template.gtm.id}');</script>
<!-- End Google Tag Manager -->
{/if}
{include file="_partials/javascript.tpl" javascript=$javascript.head vars=$js_custom_vars}
{* TODO: Cargar solo si esta definido en variable de plantilla *}
{*include file='_partials/javascript-'|cat:$djv_project|cat:'.tpl' javascript=$javascript.head vars=$js_custom_vars*}
{/block}

{block name='hook_header'}
{$HOOK_HEADER nofilter}
{/block}

{block name='hook_extra'}{/block}
<meta name="facebook-domain-verification" content="fki799u2ilw1twnjx30giavgr5qnns" />


¡MUCHA SGRACIAS!

Muchísimas gracias como siempre 4ngeluxpunk ¡Ya funciona bien!

El módulo gratuito que hay para prestashop de Google no sirve para Analytics 4, es para la antigua versión que eliminan el año que viene. Lo mejor es meterlo a mano con el literal al final del archivo.