Connect Backend To Frontend Based React

Need someone who have experience on connecting backend, we have built ui for frontend & backend admin, need to add function.

For Backend:
1. Make function to add product
2. Add payment gateway based stripe
3. Function handle order, assign order to deliverman
4. Deliveryman function, will handle order, mark order completed

For Frontend:
1. Show product added on backend to frontend
2. Show payment gateway on checkout

Technology used:
React, Nextjs