My while loop won't work even though VALUE is true?

Hello there! Your issue is common to many and unique to none. We should be able to get your script working pretty quickly. I'll just list the issues here for a quick overview:

• You assume that a while loop keeps checking after the condition is determined to be false.

• You are using KeyDown, a deprecated event.

• You are defining the character through the workspace, which is not good practice.

• You have a wait(5) at the top of your script for no reason.

• I couldn't find anything about LowerTorso. I'm not sure if it exists. I'll be using the HumanoidRootPart instead.

Now that I've listed the problems, let's go about solving them. First of all, your while loop will stop checking the condition once it's false. Here's a simpler example so you can see why:

local x = 1
while x < 5 do
	x = x + 1
	print(x)
end
print("loop is done")
x = 3
-- Nothing else prints

As you can see, this won't work for what you are trying to do. There are two alternatives to your problem (I will include examples at the end of my answer):

1.) Put the while loop in a function that is called whenever q is pressed.

2.) Put the while loop in the event listener directly.

The next problem is that you are using KeyDown, a deprecated event. If you look here, you can see a message that says, "Mouse events have been superseded by UserInputService which should be used in all new work." Clearly, we are intended to use UserInputService instead. For this answer, I'm just going to cover how to detect a key being pressed(If you want a button to pop up for a mobile user, you may want to consider using ContextActionService instead). Here's an example of how you would implement UserInputService to detect the q key being pressed with InputBegan:

--[[
	GetService is the recommended method 
	for getting services, especially on the client.
--]]
local userInputService = game:GetService("UserInputService") 

userInputService.InputBegan:Connect(function(inputObj, gameProcessed)
	if not gameProcessed and inputObj.KeyCode == Enum.KeyCode.Q then
		print("Pressed")
	end
end)

Quick note about the gameProcessed parameter from the API reference:

Indicates whether the game engine internally observed this input and acted on it. Generally this refers to UI processing, so if a button was touched or clicked from this input, gameProcessedEvent would be true. This is also true for input events connected via ContextActionService.

Finally, that wait(5) at the top of your script is unnecessary. If you're using the proper methods in their proper places, there is no need to yield. You can use the :Wait() method of the CharacterAdded event to wait for the character to load in, if it hasn't already.

Ok, here you are. Your final script should look like one of these two options:

--[[ Services ]]--

local players = game:GetService("Players")
local userInputService = game:GetService("UserInputService")

--[[ Variables ]]--

local player = players.LocalPlayer
local pressed = false
local character = player.Character or player.CharacterAdded:Wait()
local wall = workspace.TransparentTestWall -- define variables for things you are using
local RoundNumber = 10

--[[ Functions ]]--

local function Round(Number)
	return math.floor((Number / RoundNumber) + 0.5) * RoundNumber
end

local function changePos()
	while pressed do -- pressed == true is redundant
		print("test")

		local torsoPos = character.HumanoidRootPart.Position
		local x = hrpPos.x
		local y = hrpPos.y
		local z = hrpPos.z

		wall.Position = Vector3.new(Round(x), y+7.8, Round(z) -16.5)

		wait(0.01)
	end
end

userInputService.InputBegan:Connect(function(inputObj, gameProcessed)
	if not gameProcessed and inputObj.KeyCode == Enum.KeyCode.Q then
		print("Pressed")
		if pressed then -- I included a way to turn it off
			pressed = false
		else
			pressed = true
			changePos()
		end
	end
end)

or

--[[ Services ]]--

local players = game:GetService("Players")
local userInputService = game:GetService("UserInputService")

--[[ Variables ]]--

local player = players.LocalPlayer
local pressed = false
local character = player.Character or player.CharacterAdded:Wait()
local wall = workspace.TransparentTestWall -- define variables for things you are using
local RoundNumber = 10

--[[ Functions ]]--

local function Round(Number)
	return math.floor((Number / RoundNumber) + 0.5) * RoundNumber
end

userInputService.InputBegan:Connect(function(inputObj, gameProcessed)
	if not gameProcessed and inputObj.KeyCode == Enum.KeyCode.Q then
		print("Pressed")
		if pressed then -- I included a way to turn it off
			pressed = false
		else
			pressed = true
			while pressed do -- pressed == true is redundant
				print("test")

				local hrpPos = character.HumanoidRootPart.Position
				local x = hrpPos.x
				local y = hrpPos.y
				local z = hrpPos.z

				wall.Position = Vector3.new(Round(x), y+7.8, Round(z) -16.5)

				wait(0.01)
			end
		end
	end
end)

Personally, I prefer the former, but it's really up to you. ####I hope this helps. Have a great day scripting!