When all players teleport to lobby change walk speed?

So, you have wrote the WalkSpeed word wrong. If you have added tools in the player and you want to remove them, write this below the WalkSpeed = 16:

for i,Child1 in ipairs(v.Backpack:GetChildren()) do
    if Child1.ClassName == "Tool" then
        Child1:Destroy()
    end
end

for i,Child2 in ipairs(v.Character:GetChildren()) do
    if Child2.ClassName == "Tool" then
        Child2:Destroy()
    end
end

If you need to add the tools, put the tools in the ServerStorage and put this below the print("The game started"):

for i,Child in ipairs(game.ServerStorage:GetChildren()) do
    Child:Clone().Parent = v.Backpack
end

local h = Instance.new("Hint", workspace)
local b = Instance.new("Hint", workspace)
-- local humanoid = script.Parent:findFirstChild("Humanoid")
-- Making this a local value will only pull one Humanoid.
while true do
    for g = 10, 0, -1 do
    h.Text = "There is " ..g.. " seconds left"
    wait(1)
end
for i, v in pairs(game.Players:GetPlayers()) do
    v.Character:MoveTo(workspace.lobby.Position)
print("Players teleported!")
humanoid = v.Character:FindFirstChild("Humanoid") -- If we put it here, then it'll find the humanoid of the current Character.
humanoid.WalkSpeed = 16
stuff = v.Backpack:GetChildren()
v:Destroy()
end
wait(1)
for t = 10, 1, -1 do
h.Text = "Intermission " ..t
wait(1)
end
for i, v in pairs (game.Players:GetPlayers()) do
    v.Character:MoveTo(workspace.SpeedBrick.Position)
    tool = game.Lighting.TOOLNAMEHERE:clone() -- Put the tool in lighting and replace TOOLNAMEHERE with the Tool's name.
    tool.Parent = v.Backpack
    print("Game started")
end
end