i have this line of code and its supposed to make me faster why?

local speedBoost = script.Parent

local function steppedOn(part)
	local parent = speedBoost.Parent
	if game.Players:GetPlayerFromCharacter(parent)then
		parent.humanoid.walkspeed = 50 
	end
end

speedBoost.Touched:Connect(steppedOn())

You can't run functions in a connection, all you have to do is remove the () from the steppedOn function on line 10.

local speedBoost = script.Parent

local function steppedOn(part)
    local parent = speedBoost.Parent
    if game.Players:GetPlayerFromCharacter(parent)then
        parent.humanoid.walkspeed = 50 
    end
end

speedBoost.Touched:Connect(steppedOn)

In Lua things are case-sensitive, meaning you should use Humanoid and WalkSpeed, not humanoid and walkspeed. Also, when connecting a function to a RBXScriptSignal, you must only put the function's name, not following by the ().

local speedBoost = script.Parent

local function steppedOn(part)
    local parent = speedBoost.Parent
    if game:GetService("Players"):GetPlayerFromCharacter(parent) then
        parent.Humanoid.WalkSpeed = 50 
    end
end

speedBoost.Touched:Connect(steppedOn)