I can help you built the Web API for your SQL Server DB with the following methods:
Sign up: FName, LName, Username, Phone, Password, Email
Sign In: with email/username and password
signUpActivity will be connected with the SignUp method, similarly, signInActivity will be connected with the SignIn method, and mainActivity Shows welcome FName, LName for the user after accessing by SignIn
I am sure I can implement all of your requirements.
I can start on your project immediately and let me know if you would like to discuss anything further with me.
Thank you and looking forward to hear from you soon.