You can add a custom domain to your web app using your own domain.
You can add a script to your website home page so that it redirects to your web app when users view your website on a mobile or tablet.
Use your website’s API to add products with eCommerce capability into your app.
For the technical, you can create a json API for your website and add the url to read all your products directly into your app.
Create an API to read the gallery from your website directly to your app by adding your api url only. Data will be displayed in real time.