Why my score doesent adding?

Here it is. I have no clue,why it doesent adding.
P.S i have a script,where if you click left mouse button,it shows u name of the object and amount of score,but why this score doesnt adding? Like i ‘‘picked up’’ one object,it showed me “Cube,+1”,than i picking up Sphere,it showed me “Sphere,1” Why amount of points doesnt added like 1+1…

using UnityEngine;
using TMPro;

public class Informator : MonoBehaviour
    private string _Name { get; set; }

    private int _Score { get; set; }

    public TMP_Text nameText;
    public TMP_Text scoreText;

    private void OnMouseDown()

    void ShowName()
        _Name = gameObject.name;
        nameText.text = _Name;

    void ShowScore()
        scoreText.text = _Score.ToString();