mobile app android and ios connecting with API our webpage and chatgpt

I’m looking to create a mobile app for both Android and iOS that integrates with an API from our website and a chatbot. Unfortunately, the API needs to be developed and I’m looking for someone to help with that. Additionally, as I don’t have a specific design for the app, I need the freelancer to create the design from scratch. Furthermore, besides connecting to the API and chatbot, I also want the app to have user registration/login features. I’m ultimately looking for a reliable freelancer who can provide quality work in a timely manner.