How can i make it so when i click a block a different block disappears and i can walk through it?

Assuming that you want to click a block with a click detector First

-Add a click detector to the part that youd like to click and and name it "Button"

-Name the part youd like to go transparent "Door"

After that you can use this (Add this script to the inside of a model including the button and the door.)

--Variables
local Button = script.Parent.Button.ClickDetector
local Door = script.Parent.Door
local TransparencyVar = .6
local DoorOpeningTime = 5
--Transparency can but set inside of the event but for simplicitys sake we'll have a variable for it. Transparency can be from 0 to 1, 1 being completely transparent, 0 being not at all transparent.
--The same goes for DoorOpeningTime, but the number is in seconds of how long youd like to wait.
Button.MouseClick:Connect(function()
	Door.Transparency = TransparencyVar
	--Uses the Transparency variable we defined earlier
	Door.CanCollide = false
	wait(DoorOpeningTime)
	--Uses the Delay we set earlier of 5 seconds.
	Door.Transparency = 0
	Door.CanCollide = true
end)