How can i fix this problem with this local sprint script i am editing?

I was trying to edit SprintScript to make it enable effects for local player. It works in studio, but it doesnt work in game (Effects dont appear, it only changes WalkSpeed,FoV and JumpPower, puts sprint feature into infinite loop after i press shift while i am in game)

local mouse = game.Players.LocalPlayer:GetMouse()
local running = false

function getTool()  
    for _, kid in ipairs(script.Parent:GetChildren()) do
        if kid.className == "Tool" then return kid end
    end
    return nil
end


mouse.KeyDown:connect(function (key) -- Run function
    key = string.lower(key)
    if string.byte(key) == 48 then
        running = true
        local keyConnection = mouse.KeyUp:connect(function (key)
            if string.byte(key) == 48 then
                running = false
            end
        end)
        for i = 1,5 do
            game.Workspace.CurrentCamera.FieldOfView = (160)
            wait()
        end
        game.Players.LocalPlayer.Character.Humanoid.WalkSpeed = 248
        game.Players.LocalPlayer.Character.Humanoid.JumpPower = 250
        game.Workspace.CurrentCamera.CC.Enabled = true
        game.Workspace.CurrentCamera.Blur.Enabled = true
        game.Players.LocalPlayer.PlayerGui.Sound:Play()
        game.Players.LocalPlayer.PlayerGui.Peace:Stop()
        game.Players.LocalPlayer.PlayerGui.Run.Enabled = true
        repeat wait () until running == false
        keyConnection:disconnect()
        game.Players.LocalPlayer.Character.Humanoid.WalkSpeed = 12
        game.Players.LocalPlayer.Character.Humanoid.JumpPower = 50
        game.Workspace.CurrentCamera.CC.Enabled = false
        game.Workspace.CurrentCamera.Blur.Enabled = false
        game.Players.LocalPlayer.PlayerGui.Run.Enabled = false
        game.Players.LocalPlayer.PlayerGui.Sound:Stop()
        game.Players.LocalPlayer.PlayerGui.Peace:Play()
        for i = 1,5 do
            game.Workspace.CurrentCamera.FieldOfView = (70)
            wait()
        end
    end
end)

How can I fix it?