how can i use AVFoundation to add an overlay layer over a video and write text in that layer which keeps changing every 5 secs

Question

i am using AVFoundation to edit video in ios. I want to add a overlay layer which shows text above the videoView and that text should keep changing after every given time interval(let us suppose 5 secs)

let asset = AVURLAsset(url: videoURL)
    let composition = AVMutableComposition()
    
    guard
      let compositionTrack = composition.addMutableTrack(
        withMediaType: .video, preferredTrackID: kCMPersistentTrackID_Invalid),
      let assetTrack = asset.tracks(withMediaType: .video).first
      else {
        print("Something is wrong with the asset.")
        onComplete(nil)
        return
    }
    
    do {
      let timeRange = CMTimeRange(start: .zero, duration: asset.duration)
      try compositionTrack.insertTimeRange(timeRange, of: assetTrack, at: .zero)
      
      if let audioAssetTrack = asset.tracks(withMediaType: .audio).first,
        let compositionAudioTrack = composition.addMutableTrack(
          withMediaType: .audio,
          preferredTrackID: kCMPersistentTrackID_Invalid) {
        try compositionAudioTrack.insertTimeRange(
          timeRange,
          of: audioAssetTrack,
          at: .zero)
      }
    } catch {
      print(error)
      onComplete(nil)
      return
    }

let videoLayer = CALayer()
    videoLayer.frame = CGRect(origin: .zero, size: videoSize)
    let overlayLayer = CALayer()
    overlayLayer.frame = CGRect(origin: .zero, size: videoSize)

how i can add text to overlayLayer such that every 5 secs the text gets changed.

i have tried using this function

private func add(text: String, to layer: CALayer, videoSize: CGSize) {
    let attributedText = NSAttributedString(
      string: text,
      attributes: [
        .font: UIFont(name: "ArialRoundedMTBold", size: 60) as Any,
        .foregroundColor: UIColor.red,
        .strokeColor: UIColor.white,
        .strokeWidth: -3])
    
    let textLayer = CATextLayer()
    textLayer.string = attributedText
    textLayer.shouldRasterize = true
    textLayer.rasterizationScale = UIScreen.main.scale
    textLayer.backgroundColor = UIColor.clear.cgColor
    textLayer.alignmentMode = .center
    
    textLayer.frame = CGRect(
      x: 0,
      y: videoSize.height * 0.85,
      width: videoSize.width,
      height: 150)
    textLayer.displayIfNeeded()
    
    layer.addSublayer(textLayer)
  }

but text doesn't change.