Display Screen or Portion Thereof with an Animated Graphical User Interface

FIG. 1 is a front view of the first image in a sequence for a display screen or portion thereof with an animated graphical user, according to a first embodiment of the new design; FIG. 2 is a front view of the second image thereof; FIG. 3 is a front view of the third image thereof; FIG. 4 is a front view of the first image in a sequence for a display screen or portion thereof with an animated graphical user, according to a second embodiment of the new design; FIG. 5 is a front view of the second image thereof; and, FIG. 6 is a front view of the third image thereof. The appearance of the transitional image sequentially transitions between the images shown in FIGS. 1 - 3 and 4 - 6 . The process or period in which one image or portion thereof transitions to another forms no part of any of the claimed designs. The broken lines shown in the form of dash-dot-dash lines, which define the bounds of the claimed design, form no part of the claimed design. Neither the display screen nor portion thereof nor any aspects of the graphical user interfaces shown in broken lines (including in the form of dash-dash lines) forms any part of any of the claimed designs. In all of the figures, the outermost broken lines forming a dash-dash line pattern represent a display screen or portion thereof, and form no part of any of the claimed designs.