Honestly, that's pretty slow. I would guess you are doing something wrong technique-wise in your turns. There are loads of good threads on here about improving your shuttle run time. Do a search and see if you can improve your technique a bit, that will pay off far more than trying to run faster with the wrong turning technique. It is all about timing the turn and decelerating/accelerating as rapidly as possible. Good luck!
The way you turn affects your time... DS couldn’t get better than 10.5 until he talked to his PE teacher, found out his technique was wrong and he was turning too slow.... 15 min of coaching and few days of practice he was able to do 8.9 on actual test... I’d say video record and analyze with a knowledgeable person, it can be easily improved by 1.5 - 2 seconds. Good luck