How do you believe an anarchist society should be?

Obviously this is an anarchist subreddit, so you all want anarchy. But im more interested in details and explanations as to how this all should work.

How would crime investigation and solving work in an anarchist.. country? Wouldnt terrible people be able to run rampant since there are no rules..?

If theres no borders, what would be done about countries that want to invade and take space? You would need organization and communication for that.

Those are just a couple questions.