Can You share a Quest with someone who has completed it?

Hiyas...Im fairly new to the game, and was playing with a friend this weekend. He has played the game more than I have and has already completed most of the primary quests. Well i asked for his help with one of the primary quests and on my mini map it showed the Green arroe and green star locations, but didnt show it to him. I was wondering if there was a way for him to see these quest directions on his minimap?

The only way is for him to have the quest. That's just how it works, so you'd have to give directions to aide him.

When I go back to help someone I ask them to lead the way (since I don't have the green arrow and star), unless I remember the quest well enough.

you will just have to lead, although you can ping locations on the radar map my clicking on it or draw arros and things by click+dragging on the radar.