Hi, newbie to having a bonsai. We were given a buxus and it was doing well until recently. Was unsure if too much sun or not enough water. We've scratched the branches and there's some green under there. Any advice on what to do?? Or is it a lost cause outside bonsai. Thanks 

This tree is dead.

Yes very dead. Box need a lot of water and mainly shade, they do not like a lot of direct sun. That would not kill it, lack of water will.