Display Screen or Portion Thereof with a Graphical User Interface

A portion of the disclosure of this patent document contains material which is subject to copyright protection. The copyright owner has no objection to the facsimile reproduction by anyone of the patent document or the patent disclosure, as it appears in the Patent and Trademark Office patent file or records, but otherwise reserves all copyright rights whatsoever. The FIGURE is a front view of a display screen or portion thereof with a graphical user interface. The dashed broken lines depict portions of the display screen or portion thereof with a graphical user interface that form no part of the claimed design.