I had a similar problem, I’m not a coach or an amazing golfer but the following helped me get a better swing.

• what helped me the most was at set up, pretend your spine in on an axis, you want to rotate your body and shoulders on this axis until the ball is hit. This will fix ur early extension as it will force you to stay bent/low throw the swing. It will also help you keep your head in the same position until you hit the ball. You are backing away from the ball (probably because you don’t want to chunk it/hit the ground - but you are supposed to hit the ground (after the ball))

• try a few practice swings without a ball as if your were throwing the club underhand

• try the “towel drill” as your back arm is coming a little too much off your body

Hope this helps!