If i start a youtube list and work in another tab, i had to start every song manually, because after each song it stopped. please help!

Let's assume you already play an "youtube playlist" on Safari . You open a different tab within Safari whilst your playlist is playing. Drag up outside the youtube tab from the main window, similar as you have 2 Safari windows open, hopefully makes sense. Next step just go with your youtube window into a different Mac Window , and put it in full screen. And that's it , you won't have any other problem. Literally, play youtube into a different standalone Safari Window into a different Mac Desktop Window in Full View.