PrestaShop

Install GTM plugin: Go to plugin 
 In the plugin, enter the Google Tag Manager ID GTM-KK8SCVP 
 Configure all settings as shown in the images: 
 
 If you do not wish to purchase the GTM plugin, the datalayer can also be provided directly by Shoplytics. However, this requires custom programming for your shop (which will then be loaded directly via the Shoplytics script). The Shoplytics datalayer service is slightly cheaper than the GTM plugin and can be booked at https://www.checkout-ds24.com/product/592227/.