continue working on a mobile app

have a Good knowledge with Node.js, (MongoDB for the server.)
2. Knowledge with React Native

our app is like a social media app its 80% done. What I will need is

1- linking the application with the backend server.
2- require few API changes to add/delete/like/dislike a post
3- require few API changes to change user profile data.
4- Create APIs for direct messages between users,

thank you in advance