Hi Jes.
To remove he Clutch centre nut you need to lock the clutch basket outer with the inner, you can buy a tool or make one by clamping two clutch plates together (Drive plate and plain plate). Regarding the crank nut, first remove the split pin if fitted, you can buy a tool, which is a C type spanner, or use a soft metal drift, you will need to lock the engine, as these nuts can be tight.