如何实现auth flow in react native with react navigation？

Hi guys need help over Login flow, I write a code for auth flow but facing some weird issue like. Right now what is happening I have login page while clicking on signIn button, I am sending the user to auth screen but if user click on back button then he moves to login screen again, and this is wrong, if user is login then why it's again move to login screen.Hi guys need help over Login flow, I write a co