Wordpress as a frontend website for iOS app

I am developing a product for a local gym. The product comes in 2 parts : - a smartphone app used by the client - a website used by the coach

The coach uses the website to prepare the workout. So I need a good UI to allow him to create it. I can think a list of exercises from which he can selects the exercises, a form to set various parameters like the weight used for each set, etc.

So this data can contain integers, pictures, and text. On the other hand, the app fetches this data and works with it. That is, the user trains and records his perfs on the phone. At the end of the workout, the app sends the results back to the server, and the coach must be able to review it.

I have done an iOS app that deals successfully with the data and does its stuff during the training.

But I am struggling with the website since I do not know anything (almost) about web technologies. I looked into Wordpress as a mean to create both the front end and the server-database part.

I think that I need to create custom post types, like a type 'Exercise', a type 'Set', a type 'Workout' and custom meta boxes to let the coach configure the workout. But I do not know where to start.

Any guideline or advice would be greatly appreciated !