Hi,
I have over 25 years experience in programming with more than 15 years in web development and quite some years with mobile apps.
As far as I understand you want to have some kind of audio app developed, where the user can register with eMail or login with Facebook/Google. After that he/she can only select 2 audiofiles in 15 days, play them (with position remembering), review them, share them and so on.
Please contact me with so we can talk more about the specifics.
I follow the "agile development" approach - meaning, that through the entire process I update you with new versions, as soon as it has some major changes / new functions. You can than check the progress and we can talk about how you like it and what has to be changed.
I would start with a MockUp - setting up the user interface for the app, every button, ... will be there but with dummy data and clicking buttons will not do anything (in most cases).
Then I will make this app alive by adding functionality.
You can find some of my previous work in my portfolio here on freelancer.com
I will be happy to hear from you soon.
Best regards,
Fabian