The problem to solve simple UX task

I am writing to you in the hope of receiving an answer to my question. Now I'm starting to study their design and can not solve one task. I hope that you will help me to understand it.

Unfinished task

The idea of the application: Order of on-demand services

Description of the application:

1). ‘Freelancer’ (gardener, carpenter, electrician, plumber, locksmith and etc.) after registration in the app provides the following information: credit card details; photo the document proving the identity; list of services that he can provide.

2). "Сlient" is registered in the same application in order to find who could, for example, repair a chandelier in the living room.

3). With the help of the card "Client" finds the nearest electrician (our "Freelancer"), looks at his profile, checks his document, reads reviews and leaves a request, indicating the address and time, when he will be at home and pays for the ordered service (money "freeze" on the freelancer account until confirmation).

4). At the appointed time "Freelancer" comes to the «Client" does work and requests through the application confirmation performance of work at the ‘Client’.

5)."Client" receives notification, opens the application and confirms the performance of the work (after that the money transfer to the account of "Freelancer") and leaves feedback (if desired). If freelancer did not come at the appointed time, money automatically return to the Customer and the order is canceled.

The task:

Indicate potential risks and suggest improvement of logic.