You're not getting any results or logs after console.log('Img ') because you're not chaining the promise properly. You must call the getDownloadURL() before chaining .then(). See code below:

const task = firebase.storage().ref('/hendingar/' + img.name).put(img)

// Uploads the file to Firebase Storage.
task.then((snapshot) => {
  console.log('Img')
  // You can also put the creation of Firestore Document here.
  // (If you want it to create the document before getting the download URL.)
  
 // Calls the `getDownloadURL()` method.
 snapshot.ref.getDownloadURL()
  .then((url) => {
    // Returns the Download URL from Firebase Storage.
    console.log('Url')
    console.log(url)
    
    // You can put this either here or before getting download URL.
    firebase.firestore().collection('hendingar').add({
      title: title,
      description: description,
      start: start,
      end: end,
      place: infoPlace,
      prices: temp_arr,
      img: url,
    }).then(() => {
      console.log('Success')
    }).catch((error) => {
      console.error(error)
    })
  })
})
.catch((error) => {
  // Logs error if there's an error uploading of file.
  console.log(error)
})

I leave some comments on the code above for better understanding. For more information, you may checkout this documentation.