Your "navel" is your belly button, tummy button, whatever you want to call the little hole in your skin below your ribcage. "Navel gazing" is a phrase used to show that someone/a group of people is/are being too introspective and only looking inwards. That is not a good thing when what is required is a more outward-looking approach.
So the European leaders are spending too much time talking about what has already happened and looking only within Europe and, perhaps, only within their own particular country, instead of looking to the future and around them at other parts of Europe and the rest of the world.
Student or Learner