Hi. I think it is not redundant. 나의 친구와 함께한 점심. 오늘 점심은 제 친구 로란앙과 같이 먹었어요. '와/과' is postposition. '와/과' does not mean together. For example. 나는 아내와 따로 그 영화를 보았다. --> My wife and I watched the movie at the different time. To sum it up, '와/과' does not have meaning. I think the postposion is one of the biggest differences between English and korean. In English the position of each word is very important. S+V+O But in korean position of each word is very flexible because of the postposition.

In principle every noun requires a connecting particle in order to connect with a verb, adverb or noun. In the following sentences, 나의 친구와 함께한 점심. 오늘 점심은 제 친구 로란앙과 같이 먹었어요 같이 or 함께 is a adverb and can be omitted 와/과 is a connecting particle and cannot be omitted 나의 친구와 한 점심. is correct 오늘 점심은 제 친구 로란앙과 먹었어요 is correct 나의 친구 함께한 점심. is not correct 오늘 점심은 제 친구 로란앙 같이 먹었어요 is not correct In a view of redundancy, 함께 or 같이 is redundant and used for emphasizing 와/과.

Hmm, these don't seem redundant to me. 와/과 take on the meaning of "with" when used with 함께 so 친구와 함께 naturally translates to "together with friend". Also in this case, 같이 doesn't mean "with", it means "like, alike, together", so 와/과 같이 also seems natural.

Sometimes, we just need to ignore the individual grammar parts, when we look at Korean, because it may not translate directly into English. Yes, you are somewhat right and somewhat wrong. It's the natural way the structure is formed in Korean, and the way it's spoken. You may have similar thoughts on phrases like "잠을 자다", which sounds like "sleep sleep", when you first look at it, it does not translate into English very well, because we would think just "자다" should be enough. Don't necessarily think about English, think about the meaning in Korean, and you'll understand it better going forward.