How can i make a blocking move?

There are a few ways you can do this but the one I recommend is to make the change inside of the damaging script. For example...

-- Place this wherever you are removing the players health and make changes based off how your script works in the "YourWayOfCheckingHere, and Damage" sections

if player.Character.YourWayOfCheckingHere then
	player.Character.Humanoid:TakeDamage(Damage/2) -- The player is blocking and so it will reduce the damage by half
else
	player.Character.Humanoid:TakeDamage(Damage/) -- The player is not blocking and it will take the normal ammount of damage
end