The ornamental design for a displayscreen or portion thereof with a graphicaluserinterface, as shown and described.
FIG. 1 is a front view of a display screen or portion thereof with a graphical user interface, showing our new design, according to a first embodiment thereof.
FIG. 2 is a front view of a display screen or portion thereof with a graphical user interface, showing our new design, according to a second embodiment thereof.
FIG. 3 is a front view of a display screen or portion thereof with a graphical user interface, showing our new design, according to a third embodiment thereof.
FIG. 4 is a front view of a display screen or portion thereof with a graphical user interface, showing our new design, according to a fourth embodiment thereof; and,
FIG. 5 is a front view of a display screen or portion thereof with a graphical user interface, showing our new design, according to a fifth embodiment thereof.
The broken lines illustrate the display screen or portion thereof and form no part of the claimed design.