Here’s a great stretch to help you to pivot in your backswing and build flexibility so you can get a nice deep turn.
Get into your swing position with a nice, low center of gravity but still standing nice and tall. Set your left hand where you would typically grip your golf club and take your right hand underneath your wrist and get the back of both hands against each other. Apply pressure inwardly with both hands to get an isometric stretch. As you do this, engage your core and pivot so your arms begin to rotate and point away from the target.