How can i hide the created and updated field ?

[Alexander Kreß]

Is it possible to hide the two fields via Fragments or Behaviour (Script runner) ?

[Nic Brough -Adaptavist-]

Welcome to the Atlassian Community!

Not really, Behaviours is only really useful on create and edit screens, it doesn't do anything on view because Jira already hides empty fields in some of them. 

Another way to think of it is that Behaviours only affect user-editable fields, and these two are not user fields, they are informational calculated text.