Five people, one live product.
You are no longer alone. Several engineers change the same product every day, and it is serving real customers and real money. Chaos here is expensive, so the work needs discipline.
Track every change, review every change.
Git records the full history and lets people work without overwriting each other; the code lives in a shared repository. No change enters the product without another engineer reviewing it first.
Rehearse, then ship, and be able to undo.
Changes prove themselves in staging before touching production. Deployment is the controlled act of shipping, CI/CD automates the testing and shipping, and rollback (or a fast hotfix) undoes a bad release.
Change behavior without shipping code.
Feature flags turn things on and off instantly; config values differ per environment; remote config changes prices and copy without an app release, which matters most on mobile.
Know when it breaks.
Testing catches problems before users do, severity decides what gets fixed first, logs record what happened, monitoring and alerts catch trouble live, and postmortems make sure it doesn't recur. Skipped cleanup becomes tech debt.
You worked through Phase 6: run it like a company. 17 new concepts joined your architecture along the way.
Next problem: Chattogram launch: new language, new behavior, and decisions that need data.