The phrase "You murder" is probably a hyperbole. The words "murder" and "covet" are used to express how badly the people behave in order to get what they want. Alternate translation: "You do all kinds of evil things to get what you cannot have" (See: [[rc://en/ta/man/jit/figs-hyperbole]])
The words "fight" and "quarrel" mean basically the same thing. James uses them to emphasize how much the people argue among themselves. Alternate translation: "You constantly fight" (See: [[rc://en/ta/man/jit/figs-doublet]])