Display Screen with a Graphical User Interface for a Mobile Device

FIG. 1 is a front view of a display screen with a graphical user interface for a mobile device showing our new design; FIG. 2 is a bottom view thereof; FIG. 3 is a rear view thereof; FIG. 4 is left elevation view thereof; and, FIG. 5 is a right elevation view thereof. The broken lines showing a mobile device illustrate environmental subject matter and form no part of the claimed design. The broken lines showing a display screen and elements of the graphical user interface illustrate portions of the article that form no part of the claimed design.