Connect Wordpress Website DB to Android App DB and customize app landing page and fields

Hello, I have a Wordpress website that is an Events planner page, it is hosted and has its own Database (mysql) then also have an Android event also (mysql) same purpose as website and both are hosted in same Server but different DB´s. Currently they are in 2 separate DB´s with no relation but have similar and different fields . What I would need is to connect DB´s into one. so process is: What happens now is: 1. Events can be put into website backend to X DB 2. Events can be put through App backend to Y DB What I need: 3. So or the 2 DB feed one "Master" X to Z Y to Z and update back to the 2 different one´s with scheduled jobs: Z to X and Z to Y Or we unify to 1 DB, both website and app use only one (Probably the best). 4. Need to reconfigure current app to a loading page with just simple Branding and then Landing page, just with social logins and branding (already exists, just need changing theme color and putting the branding - background image). 5. Remove one field and customize and existing one (Simply changing name and fields in the database. 6. Documentation with Changes made and respective location and respective code (This for me but also for the developer if I wish future changes and or M&S) Also opened to best practice on how to handle the DB issue. Thank you in advance Cheers.