How do I change a game object's sprite in C#

I have seen plenty of similar questions, but none of them work for me.
I keep getting this error:

“Error CS0411: The type arguments for method `UnityEditor.AssetDatabase.LoadAssetAtPath(string)’ cannot be inferred from the usage. Try specifying the type arguments explicitly (CS0411) (Assembly-CSharp)”

Heres the code I use:

using System.Collections;
using System.Collections.Generic;
using UnityEngine;
using UnityEditor;

public class BallControl : MonoBehaviour {

	public float BallStartSpeed = 2f;
	public GameObject Score_1;
	public SpriteRenderer Score1Sprite;
	public Sprite Pong_N1;

	private int Score1 = 0;
	private int Score2 = 0;
	private Rigidbody2D rbBall;
	private Vector2 BallDirection;

	void Start()
	{
		Score_1 = GameObject.Find ("Score_1");
		Score1Sprite = Score_1.GetComponent<SpriteRenderer>();
		rbBall = GetComponent<Rigidbody2D> ();
		BallStart();
	}
	void Update()
	{
		if (Score1 == 1) {
			Score1Sprite.sprite = (Sprite)AssetDatabase.LoadAssetAtPath("Assets/Sprites/Pong_N1"); //This is where i get the error
		}
	}
}

What do you mean by load?