Why Schottky diode’s cut in voltage is less and the reverse saturation current is more than normal P-N junction diode?
You can look up the details, so I'll be brief and describe it only at a high level.

"Normal" diodes are a full semiconductor junction, made of P and N doped semiconductors.

Schottky diodes are sortof half a junction.  They are a semiconductor and a metal.  This as only about half the forward drop.  It also has more reverse leakage.  The metal-semiconductor junction isn't as good at blocking flow in reverse as a semiconductor-semiconductor junction.