Why the touched event takes some time to occur?

I am coding a fire ball but it should explode on direct contact with a dummy or a player but sometimes it the touched event doesn't run and other times it runs but after a delay of like 0.5 seconds. here is the code:

local damage = 40
local TweenService = game:GetService("TweenService")
script.Parent.Touched:connect(function(h)
    if h.Parent:FindFirstChild("Humanoid") and script.Parent.Value.Value~=h.Parent.Name and script.Parent:FindFirstChild(h.Parent.Name) == nil then
        h.Parent.Humanoid:TakeDamage(damage)
        print("hit and damaged"..h.Parent.Name)
        local firsthit = Instance.new("StringValue")
        firsthit.Name = h.Parent.Name
        firsthit.Parent = script.Parent
        script.Parent.Anchored = true
        damage = 15
        local tweeninfo = TweenInfo.new(
            0.5,
            Enum.EasingStyle.Quad,
            Enum.EasingDirection.Out,
            0,
            false
        )

        local partprop = {
            Size = Vector3.new(10,10,10);
            Transparency = 1;
        }
        local tween = TweenService:Create(script.Parent,tweeninfo,partprop)
        tween:Play()
        script.Parent.ParticleEmitter.Enabled = false
        wait(0.5)
        for i,v in pairs(script.Parent:GetTouchingParts()) do
            if script.Parent.Value.Value ~= v.Parent.Name and v.Name ~= script.Parent.Value.Value and script.Parent:FindFirstChild(v.Parent.Name) == nil and v.Parent:FindFirstChild("Humanoid") ~= nil then
            v.Parent.Humanoid:TakeDamage(damage)
            local thing = Instance.new("StringValue")
            thing.Name = v.Parent.Name
            thing.Parent = script.Parent
            print("damaged"..v.Parent.Name)
            end
        end
    else
        print("The player hit himself")
    end
end)