changing offset from gradual to increment

Hi everyone I have a script and I have figured out a couple of problems in it. But I still have one left in my game which is as you can see from the title I would like to change my offset animation from gradual to increment in the follow code

c# code:

 using UnityEngine;
 using System.Collections;
 
   

  public class character : MonoBehaviour {
  public float forwardSpeed = 20.0f;    
  public float rot = 0f;public float jumpSpeed = 100;public float gravity = 30f;
  public Material newMaterialRefcs1;
  public Material newMaterialRefcs2;
         
     void Start () {
  
     }
     
      void Update () {
     if( Input.GetKey(KeyCode.D)){
             transform.position += -transform.right * forwardSpeed * Time.deltaTime;
             renderer.material = newMaterialRefcs1;
             float offset = Time.time * scrollSpeed;
             renderer.material.SetTextureOffset("_MainTex", new Vector2(offset, 0)); 

     }if( Input.GetKey(KeyCode.A)){
             transform.position += transform.right * forwardSpeed * Time.deltaTime;
             renderer.material = newMaterialRefcs2;
             float offset = Time.time * scrollSpeed;


         renderer.material.SetTextureOffset("_MainTex", new Vector2(offset, 0));
  
     }
         Vector3 isgrounded = transform.TransformDirection(Vector3.up);
         if( Input.GetKeyDown(KeyCode.Space)&& Physics.Raycast(transform.position, isgrounded, 6)){
             transform.position -= transform.up * jumpSpeed * Time.deltaTime*2;
 } 
          Physics.gravity = new Vector3(0, gravity, 0);
         transform.rotation = Quaternion.Euler(0, 0, transform.rotation.eulerAngles.z);
 }
 }