Xamarin android passing and reset time between activities

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C#

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Android

Xamarin

Pass time between activity and reset from other activity
Need Help Kindly reply fast
Hi! Everyone I'm new to xamarin kindly helps me.
I want to pass time to SeeTime activity and reset time to 60 from that activity which will also reset time in the MainActivity.

What I have tried:

Code of MainActivity:

public class MainActivity : AppCompatActivity
{
public EditText timer;
Button btn;
public int elapsedTime; // counting values integer
Handler myHandler; // used to delay runnable for a second which delay_RATE
int delay_RATE = 1000; //delay
Java.Lang.Runnable r;
protected override void OnCreate(Bundle savedInstanceState)
{
base.OnCreate(savedInstanceState);
SetContentView(Resource.Layout.activity_main);
elapsedTime = 60; // default value
myHandler = new Handler(); //initializing handler
r = new Java.Lang.Runnable(Run);
timer = FindViewById(Resource.Id.timertxt);
btn = FindViewById(Resource.Id.btn1);
btn.Click += Btn_Click;
Counter();
}

private void Btn_Click(object sender, System.EventArgs e)
{
elapsedTime = 20;
StartActivity(typeof(SeeTime));
}

void Counter()
{
elapsedTime--; // increment
timer.Text = elapsedTime.ToString();
myHandler.PostDelayed(r, delay_RATE);
if (elapsedTime == 0)
{
elapsedTime = 20;
}
}
void Run()
{
Counter();
}
}

Code of SeeTimer Activity:

public class SeeTime : Activity
{
MainActivity mainActivity;
private EditText timer;
protected override void OnCreate(Bundle savedInstanceState)
{
base.OnCreate(savedInstanceState);
SetContentView(Resource.Layout.Time);
timer = FindViewById(Resource.Id.txtTime);
mainActivity = new MainActivity();
timer.Text = mainActivity.timer.Text;
// Create your application here
}
}