Display screen or portion thereof with a graphical user interface

The design consists of the visual features of the SMART PHONE WITH A DISPLAY SCREEN WITH A GRAPHICAL USER INTERFACE shown in the drawings, whether those features are one of shape, configuration, ornament or pattern or are a combination of any of these features. The portions of the drawings shown in stippled lines do not form part of the design. Drawings of the design are included, in which: Figure 1 is a front view of the SMART PHONE WITH A DISPLAY SCREEN WITH A GRAPHICAL USER INTERFACE; Figure 2 is a front view of a second variant thereof; and Figure 3 is a front view of a third variant thereof.