activate collider when button gets pressed

if (GUI.Button (new Rect(Screen.width * (5.5f / 6.55f), Screen.height * (5f / 6.3f), Screen.width * (0.85f / 6.55f), Screen.height * (0.85f / 6.3f)), “Atack”)) {
_anim.SetTrigger (_atack_0_Tr);
Handheld.Vibrate();

i want to activate collider when i press this button. If the button is not pressed collider is not active

You can enable and disable a collider of a gameobject with the following code:

        if (Input.GetKeyDown(Your key))
        {
            GetComponent<Collider>().enabled = false;
        }

You can toggle it like so:

if (// button is pressed)
{
Collider c = yourGameObject.GetComponent<Collider>();
c.enabled = !c.enabled;
}

Or you can have it active while held like so:

Collider c = yourGameObject.GetComponent<Collider>();
c.enabled = (// is button pressed);

If your script is on the same object of the collider you can use this :

if (GUI.Button (new Rect(Screen.width (5.5f / 6.55f), Screen.height (5f / 6.3f), Screen.width (0.85f / 6.55f), Screen.height (0.85f / 6.3f)), "Atack"))
{
	_anim.SetTrigger (_atack_0_Tr);
	Handheld.Vibrate();
	GetComponent<Collider>().enabled = true;
}
else
{
	GetComponent<Collider>().enabled = false;
}

else create a variable and asign it in editor

public Collider col;
if (GUI.Button (new Rect(Screen.width (5.5f / 6.55f), Screen.height (5f / 6.3f), Screen.width (0.85f / 6.55f), Screen.height (0.85f / 6.3f)), "Atack"))
{
	_anim.SetTrigger (_atack_0_Tr);
	Handheld.Vibrate();
	col.enabled = true;
}
else
{
	col.enabled = false;
}