Sprite animation on quad with UV-coordinates

I need to animate a character sprite in a 3D environment.
So far, I have created a Quad, on which I have put a material containing the (possibly malfunctioning) sprite sheet/atlas (.png). I have also attached the script below to the Quad.
I have two major challenges:

  1. The spritesheet refuses to show up as transparent in-game. Inspecting the .png-file shows the collection of sprites with the proper transparent areas. The background is either grey or a smear of colors.

  2. I have modified the script below in many ways to change the quad’s current sprite by using UV-coordinates, but I can’t figure out how to make this work properly. As of now, nothing changes in-game no matter what I set the UV-coordinates to.

Any ideas on where I might’ve gone wrong? I must’ve read 100 articles on UV-mapping by now.

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

public class UVQuadMapping : MonoBehaviour
	public Rect face = new Rect(0f, 0f, 1f, 1f);
	private float _elapsedTime = 0;
	private Mesh mesh;
	private new Vector2[] UVs;
	private int faceIndex = 0;

    void Start()
     	mesh = transform.GetComponent<MeshFilter>().mesh as Mesh;
     	Vector2[] UVs = new Vector2[mesh.uv.Length];
     	UVs = mesh.uv;
     	mesh.uv = UVs;

    void Update()
        _elapsedTime += Time.deltaTime;
        if(_elapsedTime > 1f)
        	_elapsedTime = 0;

     	mesh.uv = UVs;

    void setUVs(int pOffset = 0)
		UVs[0] = new Vector2(0, 0);
		UVs[1] = new Vector2(1, 0);
		UVs[2] = new Vector2(0, 1);
		UVs[3] = new Vector2(1, 1);

Thanks! Will gladly add more details if needed.

Hey I am also trying to do this,
can you suggest me some articles about this ,or tell me what to search in google because i am very new to unity