To update by hand a docker like netdata in my example, you need:
1 - stop current docker.
2 - recreate container:
3- Select to pull latest image:
4- wait until "recreation in progress " finalize ( can be several minutes).
Done , your docker is updated (or not if you are using latest image, but at least you know that is the latest):
Now is time to re-start the container: (button re-start on right side)
You can filter images by "used" , "Unused", filter it by unused and you can easy delete old and unused images on your system to free soace on disk: