Turn screw clockwise or counterclockwise?
Clean the track and spray it with a silicone spray which will lubricate the runners and make it easier for it to slide. This is also good for sliding windows. Ths is also good for zippers that tend to stick and will not harm the fabric.
I am not sure about the screw, but when ours became hard to slide the little acrylic roller on the bottom was worn, we popped the door out and replaced the roller and it worked fine.
If you use the spray, be sure it is silicone. Don't use WD40. It will soon become gummy and make the problem worse. If the spray doesn't help, then it is time to replace the rollers in the bottom. Glass shower door companies can do this for you if the odor is too big or heavy for you to manage. Don't wait till you injure your back trying to slide the door.
I've used WD40 with no problems. Doen;t become gummy at all. Leaves a protective waterproof coating.