Jumping, player does not come back to "ground"

Hi guys. I created a script for a player and after a while I was thinking I need him to jump as well. I tried different youtube tutorials, but no good. The only thing I can do is when I press space he will go up and never come back to “ground”. I will attach here original script without jumping, only left and right movement. How could I make him jump as well? Thank you.

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

public class Player : MonoBehaviour
{

    public Text healthDisplay;
    public float speed;
    Rigidbody2D rb;
    Animator anim;
    private float input;

    public static int health = 20;

   

    public static int score;             
    public Text scoreDisplay;     


    
    void Start()
    {
        anim = GetComponent<Animator>();
        rb = GetComponent<Rigidbody2D>();
        healthDisplay.text = health.ToString();
        scoreDisplay.text = score.ToString();      

        
    }

    private void Update()
    {
        
        if (input != 0)
        {
            anim.SetBool("isRunning", true);
        }
        else
        {
            anim.SetBool("isRunning", false);
        }

        if(input > 0)
        {
            transform.eulerAngles = new Vector3(0, 0, 0);
        }
        else if(input < 0)
        {
            transform.eulerAngles = new Vector3(0, 180, 0);
        }
        

    }



    void FixedUpdate()
    {
        
        input = Input.GetAxisRaw("Horizontal");

        rb.velocity = new Vector2(input * speed, rb.velocity.y);

        
    }

    public void TakeDamage(int damageAmount)
    {
        health -= damageAmount;
        healthDisplay.text = health.ToString();

        if (health <= 0)
        {
            Destroy(gameObject);
        }

    }


  
        


    public void addPoints(int pointsAmount)
    {
        score = score + pointsAmount;                                                 
        scoreDisplay.text = score.ToString();
    }
    private void OnTriggerEnter2D(Collider2D collision)
    {
        if(collision.tag == "Enemy")
        {                                                   
           // anim.Play("hit");
            gameObject.GetComponent<Animator>().Play("hit", -1, 0);
        }
        if (collision.tag == "Enemy2")
        {                                                    
                                                            
            gameObject.GetComponent<Animator>().Play("hit", -1, 0);
        }
    }





}

Hello There.

How is the character configured in the Inspector?

It have rigidbody? IT have “Use gravity” activated?
There are 10000 tutorials about character controlling, gravity, physics, etc… And also Download standard assets from assets store (free).

Goodluck!