Egyptologists have very good ideas of how the pyramids were built. Dressed stone, mostly ashlar, has been used to build monuments for millennia and we have murals and papyri documenting the transportation of limestone, granite, syenite etc. to construction sites. We have evidence of how they built the pyramids with cutting tools, bevels, drilling, sawing, and sanding, with harder stone being pounded or sawn into shape with abrasives. None of the pyramids are out of reach for ancient Egyptian/Kushite labor and technology, its just labor intensive and time consuming.