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 according to a first embodiment; FIG. 2 is a front view of a display screen or portion thereof with a graphical user interface according to a second embodiment; FIG. 3 is a front view of a display screen or portion thereof with a graphical user interface according to a third embodiment; FIG. 4 is a front view of a display screen or portion thereof with a graphical user interface according to a fourth embodiment; FIG. 5 is a front view of a display screen or portion thereof with a graphical user interface according to a fifth embodiment; FIG. 6 is a front view of a display screen or portion thereof with a graphical user interface according to a sixth embodiment; and, FIG. 7 is a front view of a display screen or portion thereof with a graphical user interface according to a seventh embodiment. The dashed broken lines define the bounds of the claimed design and form no part thereof. The masked area outside the broken line boundary depicts portions of the article that form no part of the claimed design. The outermost broken lines showing a display screen or portion thereof illustrate portions of the article and form no part of the claimed design.