Adding Air Velocity

Hello! I’m new to Unity.

I have a lot of the basic movement I want in my 3d game I just I need to add air velocity and slowing down the strafing in the air

My Movement code right know:

public KeyCode RunKey = KeyCode.LeftShift;
public KeyCode JumpKey = KeyCode.Space;

public float MoveSmoothTime;
public float GravityStrength;
public float JumpStrength;
public float WalkSpeed;
public float RunSpeed;

private float CurrentSpeed;
private CharacterController Controller;
private Vector3 CurrentMoveVelocity;
private Vector3 MoveDampVelocoty;

private Vector3 CurrentForceVelocity;

void Start()
{
    Controller = GetComponent<CharacterController>();
}

void Update()
{
    Ray groundCheckRay = new Ray(transform.position, Vector3.down);

    Vector3 PlayerInput = new Vector3
    {
        x = Input.GetAxisRaw("Horizontal"),
        y = 0f,
        z = Input.GetAxisRaw("Vertical"),
    };

    if (PlayerInput.magnitude > 1f)
    {
        PlayerInput.Normalize();
    }

    Vector3 MoveVector = transform.TransformDirection(PlayerInput);
    CurrentSpeed = WalkSpeed;
    if(Input.GetKey(RunKey) && Input.GetAxis("Vertical") > 0f)
    {
        CurrentSpeed = RunSpeed;
    }

    CurrentMoveVelocity = Vector3.SmoothDamp(
       CurrentMoveVelocity,
       MoveVector * CurrentSpeed,
       ref MoveDampVelocoty,
       MoveSmoothTime
       );

    Controller.Move(CurrentMoveVelocity * Time.deltaTime);

    if (Physics.Raycast(groundCheckRay, 1.1f))
    {
        CurrentForceVelocity.y = -2f;

        if (Input.GetKey(JumpKey))
        {
            if (Input.GetKey(KeyCode.S) && Input.GetKey(JumpKey))
            {
            }
            else if (Input.GetAxis("Vertical") > 0f)
            {
                CurrentForceVelocity.y = JumpStrength;
            }
        }
    }
    else
    {
        CurrentForceVelocity.y -= GravityStrength * Time.deltaTime;
    }

    Controller.Move(CurrentForceVelocity * Time.deltaTime);
}

For any help I would be grateful I’ve been on Unity for less than a month so tell me any big mistakes and criticism they would be very helpful.