Hi, My name is Hasnain. I've read and understood the project specifications, just for clarification your business is up and running as you've mentioned and you need to an android app for users and backend to process requests made by users. I'm available to work on this project and will try my best to deliver in 20 days because the project contains backend and frontend both so is huge. I'm not a native Android developer. I'll be developing this app in React Native which will eventually give you the final app for both platforms (Android & iOS)
As for my technical background, I've over 3 years of software engineering experience. I'm currently working as a software engineer in a Swedish company here in Pakistan. I mostly use Python and PHP for my web development projects. I've worked on several mobile apps by projects powered by React Native.I've experience in web frontend development stacks including Angular, React & jQuery as well. I'd love to get more details from you about the project, send me a message.