Extra trailing closure passed in call

There are many other errors here.

Why do you need a UIViewRepresentable ? If you need it, it is not complete, you need to define func updateUIView

Your ButtonView has no trailing closure in its definition. What do you try here ? You should call

                ButtonView()

and define the action in ButtonView

UIButton is incorrect. Use

                Button ("Sign up") {

You'd better learn more on SwiftUI before continuing.