Display Screen or Portion Thereof with Graphical User Interface

FIG. 1 is a front view of a first embodiment of a display screen or portion thereof with a graphical user interface showing our new design; FIG. 2 is a front view of a second embodiment of a display screen or portion thereof with a graphical user interface showing our new design; and, FIG. 3 is a front view of a third embodiment of a display screen or portion thereof with a graphical user interface showing our new design. The dash-dot broken lines in the drawings illustrate the display screen or portion thereof and form no part of the claimed design. The remaining broken lines in the drawings illustrate portions of the graphical user interface that form no part of the claimed design.