Hello, jus to update finally my login script worked, the process i did is as per following
1. Screen1 - Google Account Picker + Firebase authentication – this gives me username and email – i pass this to API wrote on my server
2. My server - it checks whether user is present in our websites database, if no, it will create user entry into database and generate user ID in return response for API on screen 1
(on screen1 i wrote another block to featch API using web component and defined this UserID as global variable and passed this variable to screen 2)
3. Screen 2 - capturing userID from global variable and passing userID to another API which will generate session for userID and redirect user to Home page with Login session automatically
Thanks @HRIHAAN_SHAIKH-M & @Still-learning for your inputs