Wordpress expert who has experince to build api for mobile app

Hello I need to build api for mobile app. There is already existing platform which was developed using wordpress. You should build almost 30 apis. 1. Do you have experience in api work on wordpress ? If you have , show me api examples which you have made . 2. For example , for login and signup api , what is param and response ? 3. Can you custom wordpress admin panel such as ecommerce function? 4. Are you team or individual ? 5. How long does it take exactly to finish api ? Please bid who is expert. thanks