PNG keeps pixels, not the editable CorelDRAW object model
A CDR project can contain curves, text, layers, and other design objects. PNG records a raster image. It is convenient for display, but resizing the exported bitmap upward later can make edges and small lettering look soft.
Keep the original CDR file for revisions. Use the PNG as a delivery asset for a particular size, background, and context rather than as the only archival copy of the design.