How to make a basic 2d movement script for a 3d game

hello,i was making a 3d game but the character in the game is a 2d sprite and i want the sprite to have a 2d left to right walk and a jump movement script on it and the script that i put on my sprite dosent work to well because it has rigidbody and when an object has rigidbody body is needs a collider or else its gonna fall through other object so when i put a collider on my sprite it dosent go on my sprite to well and the sprite cant walk right how can i make it to where i don't need rigidbody for my sprite to walk and how can i add a jump movement to my script.

 using UnityEngine;
 using System.Collections;
 
 public class movement : MonoBehaviour {
 
     public float speed;
     
     void Awake () {
         
     }
     
     void FixedUpdate () {
         
         if (Input.GetKey("a")) {
             GetComponent<Rigidbody>().AddForce (-Vector3.right * speed * Time.deltaTime);
         }
         if (Input.GetKey("d")) {
             GetComponent<Rigidbody>().AddForce (Vector3.right * speed * Time.deltaTime);
         }
     }
 }