There are many ways to swing a golf club, many movements that can be made to work. Some things that are not optional if a swing is to be maximally efficient. Swinging the arms the right way is one of them.
The arms swing, and they swing from the shoulders. That fact is not as obvious as it sounds.
Stand up and bend over a bit so your arms hang down in front of you. Gently swing them from side to side. Notice how they move freely inside the shoulder joint. That is how arms are designed to move.
Pick up a golf club. Swing it back and forth from about 3:00 to 9:00 while concentrating on the arms moving freely in the shoulder joint like they just did. Your body needs to turn some, too, so let it.
When this exercise gets easy and familiar, move on to making full swings, back and forth without stopping, with the arms swinging freely in this way.
The golf swing is made of the arms swinging, the body turning. This is how the arms swing.