Android React Native audiobook app

I want to add some features on a project from github / transform it from an audio player to an audiobook player. (basically you can get inspired from any audiobook apps but i want it adapted for subsonic API , some apps that already have what im asking here and there are open source are Dsub app / Booksonic app ..etc. )

The app is using subsonic API and majority of the API is already included in the app so it can be done pretty fast.
The server im using is ampache server ( https://github.com/ampache/ampache )
Subsonic API: http://www.subsonic.org/pages/api.jsp
If you have any other decent suggestions for what im trying to achieve here you are welcome to share but im going for the cheapest / fastest way of doing it. (maybe you have something ready to go)

What i need added /changed: (ill share you the app link after)

Variable playback speed
Sleep timer
Continue where you left on different device? (or on same device for later)
Add option to save Bookmarks and a Bookmarks section for your saved bookmarks (it has Playlist option that can be removed and replaced with bookmarks)
Sort by year, genre, (the rest of "sorts" are already there)
Chrome Cast for audio
Android auto (if possible)
Starred separate section in menu (already has it but i just want to move it in a different tab)
Full star rating (5 star) for albums / artists (there is a simple subsonic api for that)
Artists / Album description. (when you open the specific section)
Keep screen on option.

It supports multiple servers , i want that removed and i need it to only use my server with an login/register/forgot password /logout option.
i want subscribe option , i intend to use https://stripe.com/ as i feel its the most easy to do ( i can give you developer invite on my account for setting it up)
Minimalist "My account" section with a few stats and password change option. (there is subsonic API for that)
I need you to make it more eye catching (structure wise - pictures , logos and others i can add them myself after but i dont mind if you can do it for me but i want to keep the price low )
When we done i want the app to be ready to upload to play store. (we can talk about and IOS version of it )

We can talk about the details after.