Display Screen or Portion Thereof with a Graphical User Interface

FIG. 1 is a front view of a first image in a sequence for a display screen or portion thereof with a graphical user interface;

FIG. 2 is a second image thereof;

FIG. 3 is a third image thereof; and,

FIG. 4 is a fourth image thereof.

The outermost broken lines showing a display screen or portion thereof illustrate portions of the article and form no part of the claimed design. The masked area outside the irregular broken line boundary forms no part of the claimed design. The appearance of the graphical user interface transitions sequentially between the images shown in FIGS. 1 - 4 . The process or period in which one image transitions to another forms no part of the claimed design.