How to make buttons not active when other buttons are showing

So i am working on a pause menu and decided to add a settings menu that shows up when i click the settings button but when i click the settings button the pause menu still can be seen in the backround

	void Update () 
	{
		if(Input.GetKeyDown(KeyCode.Escape))
		{
			paused = !paused;
		}
		if (paused)
		{
			PauseMenuMain.SetActive(true);
			Time.timeScale = 0;
		}
		else if (!paused)
		{
			PauseMenuMain.SetActive(false);
			Time.timeScale = 1;
		}
		if(SettingsClick == true)
		{
			PauseMenuMain.SetActive(false);
		}
		if(paused == true && SettingsClick == false)
		{
			PauseMenuMain.SetActive(true);
		}
	}

You can do it like in this tutorial

https://unity3d.com/learn/tutorials/modules/beginner/ui/ui-events-and-event-triggers

or simply use EventTriggers:

http://docs.unity3d.com/ScriptReference/EventSystems.EventTrigger.html

PS:
Time.timeScale = 0; // assign here 0.00001f;

My approach:

Put each set of menu buttons as children to a canvas object and attach them to your main Canvas as disabled.

Example:

Canvas 
-> Main [Blank Canvas]
-->--> Return to Game
-->--> Game Settings Button
-->--> Sound Settings Button
-> Game Settings [Blank Canvas]
-->--> Return to Main
-->--> Button 2
-->--> Button 3
-> Sound Settings [Blank Canvas]
-->--> Return to Main
-->--> Button 2
-->--> Button 3

When the player hits the pause button, besides pausing the game itself, the main game object should be enabled. This would enable the main menu buttons as well. Now, for the Game Settings button in main Menu, the Main Game Object is disabled, and the Game settings menu is enabled. You can use other UI elements and make this set-up as in-depth as needed, but it is still controllable and flexible. You can set-up a case structure so that a different menu is enabled on button click, and all others are disabled.