Only your hand and lower arm should move. Now slowly lower the weight back down behind your shoulder. Do that 8 to 10 times, then repeat with your left arm. This is one set. Focus on your breathing Take a few seconds to notice your breathing during your workout.
Most people do.
Trouble is, it's making your workout harder. This may sound easy, but don't be surprised if it takes you a few sessions to feel comfortable with this breathing pattern. The best trick I've found when training people is to have them count out loud as they perform a lift. They inhale naturally while lowering the weight. It's impossible to hold your breath while talking.