Andreas is a German immigrant that has come to America with his family. He comes from a wealthy family that owns a gold mining business and does not seem to understand English.
Events of Red Dead Redemption 2
Andreas and his family's camp were attacked by outlaws. He was kidnapped by some outlaws for ransom. He was saved by Arthur and Charles. He is brought back to his family. He thanks them for saving him and gives Arthur a gold bar as token of appreciation for saving him. Arthur tells Andreas to get going and he leaves with his family.
Later in the story, Arthur takes mortally wounded Eagle Flies to Wapiti Reservation he leaves it, but on his way back Arthur has a paroxysm and passes out. Before waking up in Annesburg, lying on the ground, Arthur sees the vague figures of Andreas and his wife, and hears their voices. It is unclear whether this was in fact or whether this is just another hallucination caused by a progressive disease.