How to build such a system ?

We are building a small startup but we lack some details about the tech part.

We are more like USA Instacart , I'm already building the mobile app, and chose Firebase.

The process goes as follows:

1. A user orders something.
2. The app fetches required info.
3. A Firebase function splits order into two parts.
   1. First part of order is the goods which target shop will prepare.
   2. Second part is user's info like location and payment method, and this will be sent to a delivery man who when confirms an order, will collect that order from the shop and deliver it to the buyer at their location.
4. The user receives their order and optionally give rating.

Now I've been building the public app, and want to build another app for both shops and bikers. Is that ok with two apps?

For moderators, customer service, super visors, data analysts ….. etc , I want to build something like CMS with chat capabilities for customer service .. What is the best way to make such thing?