Android Browser App Customization

I have an existing Android browser app (Kotlin, WebView) with source code and APK. I want to customize the existing app, not rebuild. Please keep all existing features and make only the following changes: Fix page loading issues when multiple tabs are open. Fix the session/logout problem so accounts do not log out too quickly. When a code is pasted, make it work across all open tabs as quickly as possible (preferably within 1 second), without breaking page loading. Remove all ID Refresh buttons. Make the Redeem button slightly smaller. Optimize the app's performance and response time as much as technically possible. Remove the "SRK Browser" title and add a small, clean custom logo. Replace the current tab system with a Chrome-like tab system, including easy tab switching and swiping. Do not change or remove any other existing features unnecessarily. If a VPN can genuinely improve the connection and stay stable, discuss before adding it. Please check the source code and APK first and confirm what changes are technically possible, the cost, and delivery time. Final delivery must include the modified APK and complete modified Android Studio source code