Android application timer and recyclerview

Hi, I am using Firebase database platform to build an Android application. Description: So far, the user is able to create a post and that post is displayed in the MainActivity as a Card View and recyclerview. I am trying to give timer for each post when users create the post so the post will display timer in the Cardview of itself and after 5 minutes it should display "time ended". Problem1: When I create two posts, timers for these two posts become same. Goal1: Each post has to have its own timer value (ex. 3 minutes) Problem2: When I click "join" button to go to other activity then come back to MainActivity, the timer textview resets. Even though you turn off the application then open it again, it resets. Goal2: When I come back from other activity, the timer textview must not reset. Even though when I restart application.