"He is not my enemy, but my friend."
Translation:Αυτός δεν είναι εχθρός μου αλλά φίλος μου.
It is not very common because it sounds like "my boyfriend". It is strange, but if you want to say "my friend eats" you don't literally say "ο φίλος μου τρώει" but "ένας φίλος μου τρώει", literally "a friend of mine eats". If that friend is present, then it's ok (but it can still sound a bit like boyfriend). I'd rather say "αυτός ο φίλος μου τρώει"