@Velvia as @Exerqtor suggests you must configure PrusaSlicer not to emit those parameters to GCode. The reason is that whoever implemented M203 (set max speeds) in Marlin ignored established precedent and chose mm/sec for the units, instead of mm/min which is standard in GCode and had been used by RepRapFirmware for several years already in M203. So if you allow PrusaSlicer to mut those commands, the maximum speeds will be forced to very low values.
