I am getting player tag not the other object that i want to destroy.

i place 7 Timer object in map and i have ninja who collect this timers;
i assign timer a tag “ExtraTime”
and ninja has a “Player” tag.

but when i hit with timer all object destroy at once. i need to destroy the only object that i collide with

this is my code

   void OnCollisionEnter(Collision collision)
{
    Timer = GameObject.FindGameObjectWithTag("ExtraTime");
    ResearchAndDevelopment.BabyCatchTimer.ElappsedSeconds += 120;
    Destroy(Timer);
}

I assume that script is on the player, in which case the Collision object passed into the OnCollisionEnter method contains information on which timer was collected. Something like this should just destroy the one timer:

void OnCollisionEnter(Collision collision)
{
    // If we hit a timer
    if (collision.gameObject.tag == "ExtraTime")
    {
        // Add time here

        // Destroy this specific timer
        Destroy(collision.gameObject);
    }
}

At the moment, you are just searching for a single timer each time there is a collision, so no guarantee it is the timer you want.