The ornamental design for a displayscreen or portion thereof with a graphicaluserinterface, as shown and described.
The file of this patent contains at least one drawing/photograph executed in color. Copies of this patent with color drawing(s)/photograph(s) will be provided by the Office upon request and payment of the necessary fee.
The FIGURE is a front view of a display screen or portion thereof with a graphical user interface showing my new design.
The long-short broken line showing of a display screen or portion thereof is included for the purpose of illustrating portions of the article and forms no part of the claimed design.