As a proficient and seasoned expert in Android application development and API integration, I'm confident that I'm the best fit for your project. I have extensive experience integrating different payment gateways, including UPI with CC AVANUE. My understanding of Google Pay, PhonePe, and Paytm, coupled with my adept troubleshooting skills, promises you a seamless integration.
Moreover, I would like to stress the fact that I'm an expert programmer in Kotlin- the language used in your app! This means a significantly reduced learning curve and an accelerated project execution for us. My commitment to quality is non-negotiable, which is why I have ensured that all the required functions for this task are ready for swift execution.
Regarding your other requirement of adding the Playstore APP UPDATE MANDATE AUTO UPDATE API -I can handle it as well. My proficiency extends to PHP too, which enables me to handle backend tasks efficiently. Looking beyond this project, a successful completion will enable me to work on future projects with you too -a win-win situation for both parties! So don't delay any further; let's get started on making your website truly seamless and efficient by incorporating these much-needed payment methods!