Custom title and sub-title text in sidebar

I have made a sidebar. I have created a login page and sign up page using firebase authentication. Now when I get logged in, I should get the email-id and name of the user as title and sub-title in the sidebar.
I am confused about how can I do that. I have 10 users registered on the firebase database.

The image shows the block of my sidebar.

Use this blocks

Every time I log in, the header title and header subtitle is going to change. I cannot keep it some fixed value. I want this value to be the email id and name which was used to signup.

At first you can use a generic title and subtitle, for example userID , user’s name and then