Can someone give me a good ai script? And how do you make one like piggy's?

I use this but it still does't work very well. Can someone help.

local myHuman = script.Parent:WaitForChild("Humanoid")
local myTorso = script.Parent:WaitForChild("HumanoidRootPart")


local clone = script.Parent:Clone()
local attackCool = true
local pathFindFails = 0
local charging = false

function checkSight(target)
    local ray = Ray.new(myTorso.Position, (target.Position - myTorso.Position).Unit * 200)
    local hit,position = workspace:FindPartOnRayWithIgnoreList(ray, {script.Parent})
    if hit then
        if hit:IsDescendantOf(target.Parent) then
            return true
        end
    end
    return false
end

function findTarget()
    local dist = 300
    local target = nil
    for i,v in ipairs(workspace:GetChildren()) do
        local human = v:FindFirstChild("Humanoid")
        local torso = v:FindFirstChild("Torso") or v:FindFirstChild("HumanoidRootPart")
        if human and torso and v.Name ~= script.Parent.Name then
            if (myTorso.Position - torso.Position).magnitude < dist and human.Health > 0 then
                target = torso
                dist = (myTorso.Position - torso.Position).magnitude
            end
        end
    end
    return target
end

function pathToTarget(target)
    local path = game:GetService("PathfindingService"):CreatePath()
    path:ComputeAsync(myTorso.Position, target.Position)
    if path.Status == Enum.PathStatus.Success then
        pathFindFails = 0
        local waypoints = path:GetWaypoints()
        for i,v in ipairs(waypoints) do
            if v.Action == Enum.PathWaypointAction.Jump then
                myHuman.Jump = true
            end
            myHuman:MoveTo(v.Position)
            if checkSight(target) and math.abs(myTorso.Position.Y - target.Position.Y) < 1.5 then
                break
            elseif (target.Position - waypoints[#waypoints].Position).magnitude > 30 then
                break
            elseif math.abs(myTorso.Position.Y - v.Position.Y) > 10 then
                break
            elseif (myTorso.Position - v.Position).magnitude > 10 then
                break
            end
            if i % 5 ==0 then
                if findTarget() ~= target then
                    break
                end
            end
            spawn(function()
                wait(1)
                if myTorso.Position.Y < myHuman.WalkToPoint.Y and 
                    (myTorso.Position - target.Position).magnitude > 10 and charging == false then
                    myHuman.Jump = true
                end
            end)
        end
    else
        pathFindFails = pathFindFails + 1 
        if pathFindFails > 10 then
            getUnstuck()
            pathFindFails = 0
        end
    end
end

function walkRandom()
    local xRand = math.random(-50,50)
    local zRand = math.random(-50,50)
    local goal = myTorso.Position + Vector3.new(xRand,0,zRand)

    local path = game:GetService("PathfindingService"):CreatePath()
    path:ComputeAsync(myTorso.Position, goal)

    if path.Status == Enum.PathStatus.Success then
        local waypoints = path:GetWaypoints()
        for i,v in ipairs(waypoints) do
            if v.Action == Enum.PathWaypointAction.Jump then
                myTorso.Jump = true
            end
            myHuman:MoveTo(v.Position)
            myHuman.MoveToFinished:Wait()
        end
    else
        wait(2)
    end
end

function getUnstuck()
    myHuman:Move(Vector3.new(math.random(-1,1),0,math.random(-1,1)))
    wait(1)
end

function chase(target)
    charging = true
    myHuman:MoveTo(target.Position)
end

myHuman.Died:Connect(function()
    wait(15)
    clone.Parent = workspace
    game:GetService("Debris"):AddItem(script.Parent,0.1)
end)

function main()
    charging = false 
    local target = findTarget()
    if target then
        if checkSight(target) and math.abs(myTorso.Position.Y - target.Position.Y) < 1.5 or
            checkSight(target) and (myTorso.Position - target.Position).magnitude < 3 then
            local dist = (myTorso.Position - target.Position).magnitude 
            if dist > 3 then
                myHuman.WalkSpeed = 12 
                chase(target)
            end
        else
            myHuman.WalkSpeed = 10
            pathToTarget(target)
        end     
    else
        walkRandom()
    end
end

while wait(0.1) do
    if myHuman.Health < 1 then
        break
    end
    main()
end