Error cs0117 physics2d does not contain a definition for overlapcircleall

using System.Collections;

public class Player : MonoBehaviour
{
    Rigidbody2D rb;
    public float speed;
    public float jumpHeight;
    public Transform groundCheck;
    bool isGrounded;
    Animator anim;
    int curHp;
    int maxHp = 3;
    bool isHit = false;
    public Main main;
    public bool key = false;

    // Start is called before the first frame update
    void Start()
    {
        rb = GetComponent<Rigidbody2D>();
        anim = GetComponent<Animator>();
        curHp = maxHp;
    }
    // Update is called once per frame
    void Update()
    {

        CheckGround();
        if (Input.GetAxis(«Horizontal») == 0 && (isGrounded))
        {
            anim.SetInteger(«State», 1);
        }
        else
        {
            Flip();
            if (isGrounded)
                anim.SetInteger(«State», 2);
        }
    }
    void FixedUpdate()
    {
        rb.velocity = new Vector2(Input.GetAxis(«Horizontal») * speed, rb.velocity.y);
        if (Input.GetKeyDown(KeyCode.Space) && isGrounded)
            rb.AddForce(transform.up * jumpHeight, ForceMode2D.Impulse);
    }

    void Flip()
    {
        if (Input.GetAxis(«Horizontal») > 0)
            transform.localRotation = Quaternion.Euler(0, 0, 0);
        if (Input.GetAxis(«Horizontal») < 0)
            transform.localRotation = Quaternion.Euler(0, 180, 0);
    }

56    void CheckGround()
    {
        Collider2D[] colliders = Physics2D.OverlapCircleAll(groundCheck.position, 0.2f);
59        isGrounded = colliders.Length > 1;
        if (!isGrounded)
            anim.SetInteger(«State», 3);
    }

    public void RecountHp(int deltaHp)
    {
        curHp = curHp + deltaHp;
        if (deltaHp < 0)
        {
            StopCoroutine(OnHit());
            isHit = true;
            StartCoroutine(OnHit());
        }
        print(curHp);
        if (curHp <= 0)
        {
            GetComponent<CapsuleCollider2D>().enabled = false;
            Invoke(«Lose», 1.5f);
        }
    }
    //Корутина, для того чтобы персонаж менял цвет при нанесении урона или смерти
    IEnumerator OnHit()
    {
        if (isHit)
            GetComponent<SpriteRenderer>().color = new Color(1f, GetComponent<SpriteRenderer>().color.g — 0.04f, GetComponent<SpriteRenderer>().color.b — 0.04f);
        else
            GetComponent<SpriteRenderer>().color = new Color(1f, GetComponent<SpriteRenderer>().color.g + 0.04f, GetComponent<SpriteRenderer>().color.b + 0.04f);

        if (GetComponent<SpriteRenderer>().color.g == 1f)
            StopCoroutine(OnHit());
        if (GetComponent<SpriteRenderer>().color.g <= 0)
            isHit = false;

        yield return new WaitForSeconds(0.02f);
        StartCoroutine(OnHit());
    }

    void Lose()
    {
        main.GetComponent<Main>().Lose();
    }

    void OnTriggerEnter2D(Collider2D collision)
    {
        if (collision.gameObject.tag == «key»)
        {
            Destroy(collision.gameObject);
            key = true;
        }

 110       if (collision.gameObject.tag == «Door»)
        {
            if (collision.gameObject.GetComponent<Door>().isOpen)
 113              collision.gameObject.GetComponent<Door>().Teleport(gameObject);
            else if (key)
                collision.gameObject.GetComponent<Door>().Unlock();
        }
    }
}

I’m a complete beginner in Unity 3D, and I’m following a video training. In the video the instructor uses the following code to open a door using raycast:

using UnityEngine;
using System.Collections;


public class HelloRaycasting : MonoBehaviour {

    bool doorClosed = true;

    // Use this for initialization
    void Start () {

    }

    // Update is called once per frame
    void Update () {

        Vector3 backward = new Vector3 ( 0, 0, -1);
        Vector3 origin = this.gameObject.transform.position;

        if (Physics.Raycast( origin, backward, 1f) && doorClosed) {
            doorClosed = false;
            GameObject.Find ("Left_Quad").transform.Translate ( new Vector3(-.8f, 0, 0));
            GameObject.Find ("Right_Quad").transform.Translate ( new Vector3(.8f, 0, 0));
        }   
    }
}

It works just fine for him. But when I try to run this on my computer I get this error:

Assets/HelloRaycasting.cs(20,29): error CS0117: ‘Physics’ does not
contain a definition for ‘Raycast’

In the end I’m not able to access none of the properties and methods of the Physics class.

I’m using Unity 5.3.2f1 (64-bit). What am I doing wrong?

I’m a beginner, but I’m thinking of making a 2D shooter.
It worked correctly until then, but when I incorporated a command to push the button of my ammunition, I threw an error.

I investigated variously, but I am not sure how to solve my problem, so I am in trouble.
Please lend me your wisdom.

error CS0117:'KeyCode' does not contain a definition for'z'

Applicable source code

public class testP: MonoBehaviour
{
    public Transform firing position;// connection with bullet
    void Update()
    {
        float x = Input.GetAxis("Horizontal");
        float y = Input.GetAxis("Vertical");
        transform.position += new Vector3(x, y, 0) * Time.deltaTime * 4f;
        if (Input.GetKeyDown(KeyCode.z))
        {
            Debug.Log("z");
        }
    }
}

What I tried

I typed it while checking each one, and tried to google the error message.
I carefully checked the commands, including capital letters, so I don’t think it’s wrong.
I changed to Space because I thought that the z key itself was useless, but this was the same.

if (Input.GetKeyDown(KeyCode.z)) {Debug.Log(«z»);}

I was able to play it just before I typed it in, and when I erased it, I confirmed that I was able to play it again.
There is no doubt that this is the cause…

Supplementary information (FW/tool ​​version, etc.)

2020.1.0f1