UICollectionViewCell auto or dynamic height

Question

hello I'm new here trying to make an app with swift. here i am trying to get dynamic cell height along with text size but i am confused, have read about preferredLayoutAttributesFitting but i can't figure it out, maybe someone can help, thank you and i really appreciate your help.

import Foundation
import UIKit
import SnapKit

class MainLv: UIView {
    
    let sampledata: [String] = ["TESTING","TESTING TESTING TESTING TESTING TESTING TESTING TESTING TESTING TESTING TESTING TESTING TESTING TESTING TESTING TESTING TESTING"]
    var mainlv: UICollectionView!
    var collectionViewFlowlayout = UICollectionViewFlowLayout()
    
    override init(frame: CGRect) {
        super.init(frame: frame)
        setuplayoutbase()
        setuplayout()
    }
    
    private func setuplayoutbase() {
        self.backgroundColor = .cColorbasegray
        self.clipsToBounds = true
        self.layer.cornerRadius = 8
        self.layer.maskedCorners = [.layerMinXMinYCorner, .layerMaxXMinYCorner]
    }
    
    private func setuplayout() {
        collectionViewFlowlayout.scrollDirection = .vertical
        collectionViewFlowlayout.minimumInteritemSpacing = 0
        collectionViewFlowlayout.minimumLineSpacing = 1
        mainlv = UICollectionView(frame: .zero, collectionViewLayout: collectionViewFlowlayout)
        mainlv.register(ViewSubCell.self, forCellWithReuseIdentifier: "CELL")
        mainlv.dataSource = self
        mainlv.delegate = self
        self.addSubview(mainlv)
        mainlv.snp.makeConstraints { make in
            make.edges.equalTo(self)
        }
    }
    
    required init?(coder: NSCoder) {
        fatalError("init(coder:) has not been implemented")
    }
}