Can somebody help me with jump script?

I tried to make a jumping script for the player, but it didn't work because it didn't match my PlayerMovement script. Anyways here's my script:
using UnityEngine;
using UnityEngine.SceneManagement;

public class PlayerMovement : MonoBehaviour
{

bool alive = true;

public float speed = 5;
[SerializeField] Rigidbody rb;

float horizontalInput;
[SerializeField] float horizontalMultiplier = 2;

public float speedIncreasePerPoint = 0.1f;

private void FixedUpdate()
{
if (!alive) return;

Vector3 forwardMove = transform.forward * speed * Time.fixedDeltaTime;
Vector3 horizontalMove = transform.right * horizontalInput * speed * Time.fixedDeltaTime * horizontalMultiplier;
rb.MovePosition(rb.position + forwardMove + horizontalMove);
}

private void Update()
{
horizontalInput = Input.GetAxis("Horizontal");

if (transform.position.y < -5)
{
Die();
}
}

public void Die()
{
alive = false;
// Restart the game
Invoke("Restart", 0);
}

void Restart()
{
SceneManager.LoadScene(SceneManager.GetActiveScene().name);
}
}

 

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