Delivery application

Question

I need to create website and mobile application that could provide to a fast food restaurant system of online transactions and deliveries, also achievement system and so on.
What I have too learn to make transaction of real money from internet and what technologies I need for website, MERN is enough?
Could I connect java front end to express server or do I need write java server too?
Also could I use react native for Android UI or should I do it?