Hey,
I can easily build an e-commerce android app with admin panel and payment gateway.
Lets start the chat so we could discuss more details easily on the project requirements for the better understanding, I have been designing and developing mobile applications for the last 7 years and I am quite confident to work on you e-commerce android app totally as per your requirements.
Kindly take a look at my portfolio from here https://www.freelancer.com/u/TheCodeSolutions
I will be waiting for the valuable response from your side, thanks.