How to Create a touch Button to move a player?

Hello People,

I am new to unity. I have build a game where there is a cube moving forward in the z-axis. The cube moves right and left to avoid colliding with obstacles. The game runs smooth when pressing Keyboard key buttons. But when I create buttons for my android phone it doesn't works correctly. When I create an event trigger for a button with (Pointer Down) and run the code, the cube will turn left when I constantly tap on the button. I have to tap 10 times in a second for it to turn right or left. I want it to be similar to the keyboard buttons where i press the button one time and everything moves smoothly. For the button event (Pointer Down) I have created this code

public Rigidbody rb;
public float forwardForce = 2000f;
public float sidewayForce = 500f;

public void Right()
{
rb.AddForce(sidewayForce * Time.deltaTime, 0, 0, ForceMode.VelocityChange);
}
public void Left()
{
rb.AddForce(-sidewayForce * Time.deltaTime, 0, 0, ForceMode.VelocityChange);
}

Here is my full player movement code:

using UnityEngine.UI;
using UnityEngine;
public class PlayerMovement : MonoBehaviour
{
public Rigidbody rb;
public float forwardForce = 2000f;
public float sidewayForce = 500f;

// Start is called before the first frame update
public void Right()
{
rb.AddForce(sidewayForce * Time.deltaTime, 0, 0, ForceMode.VelocityChange);
}
public void Left()
{
rb.AddForce(-sidewayForce * Time.deltaTime, 0, 0, ForceMode.VelocityChange);
}


// Update is called once per frame
void FixedUpdate ()
{
rb.AddForce(0, 0, forwardForce * Time.deltaTime);
if(Input.GetKey("d"))
{
rb.AddForce(sidewayForce * Time.deltaTime, 0, 0, ForceMode.VelocityChange);
}
if (Input.GetKey("a"))
{
rb.AddForce(-sidewayForce * Time.deltaTime, 0, 0, ForceMode.VelocityChange);
}

if (rb.position.y < -1f)
{
FindObjectOfType<GameManager>().EndGame();
}
}
}

 

You should not handle movement in FixedUpdate. Fixed Update runs at irregular intervals, in bursts. See the chart here:
https://docs.unity3d.com/Manual/ExecutionOrder.html

Rather than hardcoding key names, a much better idea would be to use GetAxis or GetAxisRaw, as this will handle all movement types, including gamepads.
https://docs.unity3d.com/ScriptReference/Input.GetAxisRaw.html