Hello, @Santiago,
Actually, The thing is, in our theme, there is no such possibility and features like this. But every theme worked with different plugins and can get these kinds of functionalities using third-party plugins. For example. Your business is a sales business so for this you must need the Shop plugin and that is WooCommerce, It handles all the inventory settings or products, payment methods, sales, user registrations, etc, you can check the plugin documentation here: https://woocommerce.com/documentation/ and https://woocommerce.com/search/?q=Product+Inventory&collections=documentation&page=1
https://woocommerce.com/search/?q=Payment&collections=documentation&page=1
https://woocommerce.com/search/?q=Registration&collections=documentation&page=1
https://woocommerce.com/search/?q=Shipping&collections=documentation&page=1
Now, As you said that “this functions should be integrated on buyer user management” So the buyer will be able to see shipping, addresses, and other necessary data so WooCommerce allows the customer to manage their profiles user will be able to set the address, profile picture, order history, Also If you want that user can also sell their product on your shop like as a vendor so for this you can use the “DOKAN Multivendor” plugin as well. Here is the documentation about this from our theme: https://xstore.helpscoutdocs.com/article/143-dokan-multivendor-plugin-with-xstore-theme
Other than that you can try with any third-party plugin which better meets your requirements but at your own risk.
Regards 8Themes Team.