Character Controller with Unity User Iterface input

I have script. Then i press button that walk forward character was passed some way and stopped. So I want that when i press the ui button character walk until then I pressed the button.Function "forward"and “back” I added to ui button. This make for Android.
Please help me.
Unity 5

using UnityEngine;
using System.Collections;

public class Character : MonoBehaviour 
{
	private GameObject Player ;
	public int Speed = 5;

	void Start()
		{	
			Player = (GameObject)this.gameObject;
		}

	public void forward() 
		{
			Player.transform.position += Player.transform.forward * Speed * Time.deltaTime;
		}

	public void back() 
		{
			Player.transform.position -= Player.transform.forward * Speed * Time.deltaTime;
		}
}

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