How can i make if i walked backward the walkspeed is slower

the concept are same as phantom forces if i walk normally its 16 walkspeed if i walk backward it less speed then 16. im sorry for my bad english XD

The easiest way would be to slow the character to something lower to 16 whenever they press s on their keyboard. This could be done using ContextActionService or UserInputService.

Yeah, you can change the speed when the player presses s