thanks for answering me! 
but probably not understanding you very well, But what I have done, is in my character BP I cast to the door PB when I hit something with raytrace by channel, and then run a custom event that has run on server (reliable), then that one runs interact from the door BP, but where should I turn the OnRep_ClosedOrOpen function and how on earth do I make it a rep notify? and also where do I set the closed or Open? var that has RepNotify checked?