Character and arms following player's mouse?

local tool = script.Parent.Parent
local service = game:GetService("RunService") --get  run time servise

local success = false

local player = game:GetService("Players").LocalPlayer --get the current player
local character = player.Character or player.CharacterAdded:wait() --get character
local humanoid = character:WaitForChild("Humanoid") --get humanoid

local camera = game.Workspace.CurrentCamera --player camera
local mouse = player:GetMouse() --player mouse

local offset, magnitude, vector3, cFrame, direcction = nil --varibles to make calculations
local shoulder, arm, torso, body, neck = nil --variables to hold body parts
local defaultNeckCO, defaultShoulderCO = nil --variables to hold the defauld posicion of the body parts
local animate = nil --variable to hold the function of the animation

local shoulderPositionC0, shoulderCFramePositionC1 = nil --variables to extrack some data from the body parts
local turnAngle = CFrame.fromEulerAnglesXYZ(math.pi/2, 0, 0) --constant, used later on to make calculations
local rightangle = CFrame.fromEulerAnglesXYZ(0, 0, math.pi) --constant, used later on to make calculations

local unequipListener --listener to disconect the unequip function

--get offset
function updateOffset()
    offset = (body.Position.y - mouse.Hit.p.y) / 100
    magnitude = (body.Position - mouse.Hit.p).magnitude / 80
    return offset/magnitude
end

--get vector3 of direccion
function updateBodyRotation()

    if (camera.Focus.p - camera.CoordinateFrame.p).magnitude > 1 then
        --stop the defauld rotation
        humanoid.AutoRotate = false

        --get the rotation vector3
        vector3 = Vector3.new(mouse.Hit.p.x, body.Position.y, mouse.Hit.p.z)

        --create the cframe with the same posicion of the body and the new rotation
        cFrame = CFrame.new(body.Position, vector3)

        --updating the body rotation
        body.CFrame = cFrame
    else
        --get the defauld rotation
        humanoid.AutoRotate = true
    end

end

--function to animate the humanoid R15
function animateR15()
    --update neck
    offset = updateOffset()
    neck.C0 = defaultNeckCO * CFrame.fromEulerAnglesXYZ(-offset, 0, 0)

    --update arm
    vector3 = (torso.CFrame * CFrame.new(shoulderPositionC0)).p + Vector3.new(0, -0.25,0) --offset position
    direcction = (vector3 - mouse.Hit.p).unit 
    arm.CFrame = CFrame.new(vector3, vector3 + direcction) * turnAngle * shoulderCFramePositionC1 * rightangle 

    --NOTE: the following changes update the arm in a lesser accurate way, but it's faster,
    --to change the faster way, must comments the previous update arm (previus 3 code lines),
    --and add the following code line in the "getBodyParts()" in the R15 side
    --defaultShoulderCO  = CFrame.new(1, 1, 0, 1, 0, 0, 0, 1, 0, 0, 0, 1)
    --then uncomment the following code line
    --shoulder.C0 = defaultShoulderCO * CFrame.fromEulerAnglesXYZ(-offset, 0, 0)
    --at last, the shoulder.C0 take some changes in the animation,
    --the defauld posicion have to by reset in defauld on "stopAllFunctions()", with the following code line:
    --shoulder.C0 = defaultShoulderCO
end

--function to animate the humanoid R6
function animateR6()
    --getting the offset
    offset = updateOffset()

    --update neck and arm, NOTE: this is almost the only variation between R6 nd R15,
    --and basically it's where is going to be the offset
    neck.C0 = defaultNeckCO * CFrame.fromEulerAnglesXYZ(offset, 0, 0)
    shoulder.C0 = defaultShoulderCO * CFrame.fromEulerAnglesXYZ(0, 0, -offset)
end

--function to get parts of the body depending on the humanoid
function getBodyParts()

    --same body in both humanoids types
    body = character.HumanoidRootPart

    --bifurcate between diferents humanoids to get part of the body
    if humanoid.RigType == Enum.HumanoidRigType.R15 then
        --R15

        --getting body parts
        shoulder = character.RightUpperArm.RightShoulder
        arm = character.RightUpperArm
        neck = character.Head.Neck
        torso = character.UpperTorso

        --deatach the arm
        arm.Anchored = true
        shoulder.Part1 = nil

        --setting animation
        animate = animateR15

        --Note: those CFrame are the defauld position of each motor6d
        defaultNeckCO = CFrame.new(0, 1, 0, 1, 0, 0, 0, 1, 0, 0, 0, 1)
        shoulderCFramePositionC1 = CFrame.new(shoulder.C1.p)
        shoulderPositionC0 = shoulder.C0.p
    else
        --R6

        --getting body parts
        shoulder = character.Torso["Right Shoulder"]
        arm = character["Right Arm"] 
        neck = character.Torso.Neck

        --setting animation
        animate = animateR6

        --Note: those CFrame are the defauld position of each motor6d
        defaultNeckCO = CFrame.new(0, 1, 0, -1, -0, -0, 0, 0, 1, 0, 1, 0)
        defaultShoulderCO = CFrame.new(1, 0.5, 0, 0, 0, 1, 0, 1, 0, -1, -0, -0)
    end

end


--this function try to stop all function of this script and set defauld values
function stopAllFunctions()

    pcall(function()
        --disconect the unequip tool listener
        unequipListener:Disconnect()
    end)

    pcall(function()
        --stop the rendering of the animation
        service:UnbindFromRenderStep(script.Name)
    end)

    pcall(function()
        --reset defauld position of the neck 
        neck.C0 = defaultNeckCO
    end)

    pcall(function()
        --reset the defauld rotation of the body
        humanoid.AutoRotate = true
    end)

    pcall(function ()
        if humanoid.RigType == Enum.HumanoidRigType.R15 then
            --R15 
            --atach the arm
            shoulder.Part1 = arm
            arm.Anchored = false
        else
            --R6
            --reset defauld position of the arm 
            shoulder.C0 = defaultShoulderCO
        end
    end)

end

--function to animate the character
function characterFollowTool()

    --try to render the animation
    success = pcall(function()
        --update the Bogy rotation and offset
        updateBodyRotation()

        --execute the animation, this function it's diferent depending of the humanoid type
        animate()
    end)

    --if the rendering went wrong, 
    if not success then
        stopAllFunctions()
    end

end

function onEquip()
    --add listener to the tool to stop all functions when the tool is unequipped  
    unequipListener = tool.Unequipped:connect(stopAllFunctions)

    --getting the parts of the current character
    success = pcall(getBodyParts)
    if not success then
        stopAllFunctions()
    end

    --adding the animation in the rendering of the screen
    service:BindToRenderStep(script.Name, Enum.RenderPriority.Input.Value - 1, characterFollowTool)
end

tool.Equipped:connect(onEquip)

There a script i found in toolbox. I dont know how to make the same movement but with left arm. This script only moves head, torso and right arm.