Finish Kotlin App

I currently have a Kotlin app which is done for like 85%. I need someone to finish it and help me put it in the app store (google). And if the app is a success I'd also like to have an iPhone version of the app (but that will be a later project). There is an external API with which the app communicates (self made).

The app has some functionality similar to Whatsapp (but not chatting or sending pictures or something, but other action):

- Register phonenumber (through firebase Auth)
- Sync contactlist to the external API (one way)
-> And store locally on the phone to be able to create groups and such
- Ability to add groups (view, remove (members)) etc
- Ability to do functionality on the group. Start an action (where you need to be able to 'temporarily disable certain group members for the specific action
- Retrieve messages from FireBase (for instance if someone else has done activity on the group)

The functionality needs to be checked.
Probably a little touch up on certain views (statistics)
Activating google ads on particular screen (only in production version)
Checking the code for possible improvements
Minor changes

I need a full stack developer for Kotlin to finish the project.