building an app

i have a project that has similar queries and functions to an app called getmuv, where you will have the customer make an account view gyms (because getmuv is a platform for multiple gym subscriptions and in this case it is just an example) and if he wants to subscribe he will enter his financial details. and then he can access gyms by scanning the barcode on the gym stand after subscribing. all the previous details are just an example foe the project all the technical details and actual specific instruction willl be provided later after agreement.