decyptyour meseges based on the user selected decayption method. A left shift operation should be performed for decyption.

The deay fopion method divices are as follow:

Stilitefit by $13$

Shith latit by mived keys

Sea the overview section for desciption, equation and examples for the decyption methods.

$\backslash$table$[[,],[$Puposes$,\backslash$table$[[$The function should decypt the encypted message based on the user selected decyption method$],[$anything$.]]],[$Parumeters:$,],[$Retum Value:,If successful, return the decrypted message.$],[$Enor Handing$/$Bounday Conditions:,$],[$Examples$,]]$