Good Morning Sherazi_or Salim!
Ok, with snubber components be care pls!
The capacitor must be a good "impulse foil type" and for 250VAC_sorry they are bulky, but you must have a such type...
Hes resistor can not be a 0805 or 1206 SMD too!
I must say; I dont give you a formula to calculate both, but Web has surly answer...
Its a power component, has periodically lot of currents-dissipates in both components regularly 1-3Watts
I think these is a usable script from ST, it is one of the older & bigger vendors: RC snubber circuit design for TRIACs...
PCB Trace width calculator:
**broken link removed**
It exists similar side over creepage calculations too(was some weeks ago on edaboard too), but I have to search for that...
The other aspects I will answer some later_I have to go out yet.
K.