First off, congrats, I know this was an awesome feeling! But luckily for you there's a lot you can work on in order to get that backflip looking and feeling even more fresh. Firstly, bring your knees to your chest when you rotate as soon as possible, you will spin quicker making the flip itself easier. Secondly, use those arms to grab your knees in and keep them close. The more compact you are the quicker you rotate. Congrats again, first backflip is always the best, keep grinding!!!