percentageArray = [];

startUpload(event: FileList) {

 Array.from(event).forEach(file => {
   if (file.type.split('/')[0] != 'image') {
     alert('Dieses Dateiformat wird nicht unterstützt');
   }

   // Storage path
  const path = `uploads/${this.currentUserEmail}/${this.uniqueID}/${file.name}`;

  // Meta Data
  const customMetadata = {
    auctionID: this.uniqueID.toString()
  }

   // Main Task
  this.task = this.storage.upload(path, file, {customMetadata});

  // Progress Monitoring

  this.percentage = this.task.percentageChanges();
  this.percentage.subscribe(p => {
    this.percentageArray.push(p);
  })

  this.snapshot = this.task.snapshotChanges();

  // File Download Url
  this.downloadURL = this.task.downloadURL();

  this.imgArray.push(path);

 })
}

<div *ngIf="percentageArray as item" class="w-100">
  <div *ngFor="let elem of item">
  <ngb-progressbar type="info" [value]="elem" [striped]="true" [max]="100" [showValue]="true"></ngb-progressbar>
  </div>
</div>