how do i add animation in to this sprint double tap script?

i was tried this befpre it's work but sometimes it not run the animation

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

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)
    key = string.lower(key)
    if key == "w" or key == "" then
        s = s.."w"
        delay(0.2,function ()
            if s ~= "ww" then
                s = ""
            end
        end)
        if s == "ww" then
            s = ""
            running = true
            local keyConnection = mouse.KeyUp:connect(function (key)
                if key == "w" or key == "" then
                    running = false
                end
            end)
            script.Parent.Animate.Disabled = true
            delay(0,function ()
                local stuff = script.Parent.Torso:GetChildren()
                for i = 1,#stuff do
                    if stuff[i]:IsA("Motor6D") and stuff[i].Name ~= "Neck" then
                        stuff[i].MaxVelocity = 0.3
                    end
                end
                while running == true do
                    for i = 1,#stuff do
                        if stuff[i]:IsA("Motor6D") and stuff[i].Name ~= "Neck" then
                            stuff[i].DesiredAngle = 1.5
                        end
                    end
                    if running == true then
                        wait(0.5)
                    end
                    for i = 1,#stuff do
                        if stuff[i]:IsA("Motor6D") and stuff[i].Name ~= "Neck" then
                            stuff[i].DesiredAngle = -1.5
                        end
                    end
                    if getTool() then
                        script.Parent.Torso["Right Shoulder"].DesiredAngle = 1.57
                    end
                    if running == true then
                        wait(0.5)
                    end
                end
                script.Parent.Animate.Disabled = false
            end)
            for i = 1,5 do
                game.Workspace.CurrentCamera.FieldOfView = (70+(i*2))
                wait()
            end
            game.Players.LocalPlayer.Character.Humanoid.WalkSpeed = 24
            repeat wait () until running == false
            keyConnection:disconnect()
            game.Players.LocalPlayer.Character.Humanoid.WalkSpeed = 16
            for i = 1,5 do
                game.Workspace.CurrentCamera.FieldOfView = (80-(i*2))
                wait()
            end
        end
    end
end)