Display screen or portion thereof with a graphical user interface

[0001]FIG. 1 is a front view of a display screen or portion thereof with a graphical user interface showing the first embodiment of our new design.

[0002]FIG. 2 is a front view of a second image of the first embodiment.

[0003]FIG. 3 is a front view of a third image of the first embodiment and a front view of a first image of the second embodiment.

[0004]FIG. 4 is a front view of a second image of the second embodiment; and,

[0005]FIG. 5 is a front view of a third image of the second embodiment.

[0006]The appearance of the transitional image sequentially transitions between the images shown in FIGS. 1-3 and FIGS. 3-5 respectively. The process or period in which one image transitions to another image forms no part of the claimed design.

[0007]The dashed broken line perimeter in the drawings illustrate a display screen or portion thereof and forms no part of the claimed design. The remaining dashed broken lines in the drawings illustrate portions of the graphical user interface that form no part of the claimed design.