In order to customize Shopify, you need to either learn their proprietary front-end customization language, Liquid, or hire a third-party agency that is experienced in working with Shopify.
In order to customize Shopify, you need to either learn their proprietary front-end customization language, Liquid, or hire a third-party agency that is experienced in working with Shopify. There are a large number of add-ons and extensions available from independent developers that can extend the capability of your store. All this makes it easy for Shopify to scale between small and large online stores.