Student or Learner
Troy hero, Troy's hero, Trojan hero, Which is correct and why?
By the way, can you explain to me when we use " of " and when we use " 's " in possessive case?
[a/the] hero of Troy
Trojan hero [means specifically a hero who is of Trojan origin].
You can always use "of", though it can lead to awkward phrasing.
A friend of mine/my friend
The son of my neighbour/my neighbour's son
The car of my oldest son/my oldest son's car