NPC only take away 5 health?

To add to Nexiterate - if you want the script (wait of 2 seconds) to be separate for every player who touches the brick.

local touchers = {}
local part = script.Parent


local function damage(player)
    local hum = player.Character:findFirstChild("Humanoid")
    if hum then
        hum:TakeDamage(5)
    end
    touchers[player.Name] = tick() -- Update the last time they were damaged
end

part.Touched:connect(function(hit)
    if hit and hit.Parent then 
        local player = game.Players:GetPlayerFromCharacter(hit.Parent)
        if player then 
            local index = touchers[player.Name] 
            if not index then 
                -- if player isn't even in the table yet, then damage them.
                damage(player)
            else -- if the player is in the table
                if tick() - index >= 2 then 
                    -- If the last time they were damage was more than or equal to 2 seconds, then damage them.
                    damage(player)
                end
            end
        end
    end
end)

You may achieve that using a debounce that the roblox wiki has some helpful and detailed info about what a debounce is and how to use it, you can check that out here

The code you could use is the following:

local debounce = false
function onTouched(hit)
    local human = hit.Parent:findFirstChild("Humanoid")
    if human and not debounce then
    debounce = true -- changing it to true so if the player touches it again before the two seconds have passed it would not run
        human.Health = human.Health - 5  
    wait(2) -- the function will only run if debounce is set to false, so here it waits two seconds then it reverts it back to being false
    debounce = false
    end
end

script.Parent.Touched:connect(onTouched) 

Hope it helped! If you have any questions please do not hesitate to let me know.