Im trying to create a door that you need a key to unlock, but it isnt working. How can i fix this?

First of all, i will introduce you to FOR loops. For loops are piece of code that repeats certain code for certain times... just look:

local StartValue =1
local GoalValue =10
local Increment = 1
for i = StartValue,GoalValue,Increment do
	--repeats code 10 times
end

knowing that, you can make the doorFadeOpen() function less time-requiring, or something like that:

local StartValue =1
local GoalValue =9
local Increment = 1
door.CanCollide = false
for i = StartValue,GoalValue,Increment do
	wait(0.1) --waits one tenth of a second p.s. sorry if i wrote tenth wrong
	door.Transparency = (i/10) --value being set to start value, repeating code till goalvalue and increment as the increment
end
wait(1)
door.Transparency = 0
door.CanCollide = true
--well, that saves time. i guess.

so, we will put that to the script!

local door = script.Parent
function doorFadeOpen()
	door.CanCollide = false --sets the cancollide to false, meaning you CAN pass
	for i = 1,10 do --last argument (Increment) isnt obligatory
		wait(0.1)
		door.Transparency = (i/10)
	end
	wait(2)
	door.Transparency = 0
	door.CanCollide = true --sets the cancollide to true, meaning you CAN'T pass
end

But wait... theres something wrong here... A localplayer cant be set in a server script!

local function onPartTouch(otherPart)
    local partParent = otherPart.Parent
    local key = game.Players.LocalPlayer.BackPack.Key --cant
    if key then
        door.CanCollide = false
        doorFadeOpen()
        door.CanCollide = true
    end
end
door.Touched:Connect(onPartTouch)

So, we do this:

local function onPartTouch(otherPart)
    local partParent = otherPart.Parent
    local player = game.Players:GetPlayerFromCharacter(partParent)
    if player then
'	local key = partParent:FindFirstChild("Key") --checks if key is on the character (character holding it)
	if key then --if the key exists then
     	   doorFadeOpen() --open da door!
	end
    end
end
door.Touched:Connect(onPartTouch)

I hope that helped! p.s. i take more time explaining than writing code itself :/ does that mean im a good scriptinghelpers user??