Mobile display screen or portion thereof with a graphical user interface

FIG. 1 is a front view of a first image in a sequence of a mobile display screen or portion thereof with a graphical user interface showing our new design; and,

FIG. 2 is a front view of a second image in a sequence of a mobile display screen or portion thereof with a graphical user interface showing our new design.

It should be understood that the outermost broken line rectangle showing a mobile electronics device in FIGS. 1-2 are used to illustrate environmental structure; the broken lines showing a display screen, text, and portions of the graphical user interface, are used to illustrate portions of the article; all broken lines form no part of the claimed design.

The appearance of the transitional image sequentially transitions between the images shown in FIGS. 1-2 . The process or period in which one image transforms to another image forms no part of the claimed design.