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 graphical user interface showing our design;
FIG. 2 is a front view of a second embodiment thereof;
FIG. 3 is a front view of a third embodiment thereof; and,
FIG. 4 is a front view of a fourth embodiment thereof.
The broken lines in FIGS. 1-4 showing the display screen or portion thereof and the remainder of the graphical user interface are for the purpose of illustrating environmental elements and form no part of the claimed design. The stippling shown in FIGS. 1-4 is for the purpose of showing contrast and is claimed subject matter.