Display Screen or Portion Thereof with a Graphical User Interface

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; and,

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.

The broken lines illustrate the display screen or portion thereof, and the broken lines form no part of the claimed design.