There are several texts related to the app that appear on the storefront and are therefore visible to customers. By default, most of the texts are in the Czech language, but can be customized and translated to a language of your preference. There are three locations where the texts appear - in the Shipping section of Checkout, on the Order Status Page, and on the pop-up for selecting pickup points.
Inside Checkout, the customer will see the name of the shipping method(s) tied to Zásilkovna. The name can be chosen by you at will, as long as it includes the word "Zásilkovna", "Zásielkovňa", or "Packeta" in it. You can set the shipping method in the Shopify Admin >> Settings >> Shipping and delivery.
On the Order Status Page there are a few string of text coming from the app, depending on whether or not the pickup point has been selected. You can change these texts inside the app's script that you inserted to the Checkout settings.
The pop-up to select a pickup point comes from the Packeta company itself. It has multiple language options built into it, so your customer can simply select the language of their preference. The default language of the widget is set automatically according to the language of the customer's browser.