How do I make GameObject actions ease in and out

I'm trying to make a car game with a forward and reverse mechanic that ease into its max speed and ease out into a stop. Current code: (Everything labeled)

using System.Collections; using System.Collections.Generic; using UnityEngine;

public class Movement : MonoBehaviour {

 public Rigidbody rb;
 public bool grounded = true;

 void OnCollisionEnter(UnityEngine.Collision collisionInfo)
 {
     grounded = true;
 }
 void OnCollisionExit(UnityEngine.Collision collisionInfo)
 {
     grounded = false;
 }
 
 //Start is called before the first frame update
 void Start()
 {
 }

 // Update is called once per frame
 void Update()
 {
     float MaxForwardSpeed = 20f; // maximum speed for acceleration and reverse
     float TurningRadius = 80f; // maximum speed car can turn
     float Speed = 0; // variable that changes the speed
     float Jump = 10f; // not important

     if (grounded == true) //on ground
     {
         if (Input.GetKey(KeyCode.W)) // acceleterate
         {                
             
             // ATTEMPTED GRADUAL ACCELERATION /////////////////////////////////////////////////////
             if ((Speed < MaxForwardSpeed))
             {
                 Speed += 2;
                 transform.position += transform.forward * Time.deltaTime * Speed;
             }
             Debug.Log(Speed);
             ///////////////////////////////////////////////////////////////////////////////////////

             if (Input.GetKey(KeyCode.A)) // only turns when going forward
             {
                 transform.Rotate(0, -TurningRadius * Time.deltaTime, 0);
             }
             if (Input.GetKey(KeyCode.D))
             {
                 transform.Rotate(0, TurningRadius * Time.deltaTime, 0);
             }
         }
         

         if (Input.GetKey(KeyCode.S)) // reverse
         {
             transform.position -= transform.forward * Time.deltaTime * MaxForwardSpeed;

             if (Input.GetKey(KeyCode.A)) // only turns when going backward
             {
                 transform.Rotate(0, -TurningRadius * Time.deltaTime, 0);
             }
             if (Input.GetKey(KeyCode.D))
             {
                 transform.Rotate(0, TurningRadius * Time.deltaTime, 0);
             }
         }
         
         //if (Input.GetMouseButtonDown(1))
         if (Input.GetKeyDown(KeyCode.Space)) // jump function
         {
             rb.AddForce(transform.up * Jump, ForceMode.Impulse);
         }
         if (Input.GetKey(KeyCode.LeftShift)) // air roll toggle(hold)
         {
             if (Input.GetKey(KeyCode.A)) // drift left
             {
                 transform.Rotate(0, -1, 0);
             }
             if (Input.GetKey(KeyCode.D)) // drift right
             {
                 transform.Rotate(0, 1, 0);
             }
         }
     }

     if (grounded == false) //off ground
     {
         if (Input.GetKey(KeyCode.W)) // push forward
         {
             transform.Rotate(1, 0, 0);
         }
         if (Input.GetKey(KeyCode.A)) // car turns left in air
         {
             transform.Rotate(0, -1, 0);
         }
         if (Input.GetKey(KeyCode.S)) // pull back
         {
             transform.Rotate(-1, 0, 0);
         }
         if (Input.GetKey(KeyCode.D)) // car turns right in air
         {
             transform.Rotate(0, 1, 0);
         }
         if (Input.GetKey(KeyCode.LeftShift)) // air roll toggle(hold)
         {
             if (Input.GetKey(KeyCode.A)) // air roll left
             {
                 transform.Rotate(0, 1, 0); // counters other "(KeyCode.A) movement"
                 transform.Rotate(0, 0, 1);
             }
             if (Input.GetKey(KeyCode.D)) // air roll right
             {
                 transform.Rotate(0, -1, 0); // counters other "(KeyCode.D) movement"
                 transform.Rotate(0, 0, -1);
             }
         }
     }
 }

}

• sorry so much code, I've been working on this for hours and just started using unity a day ago (don't know how to make more compact code)