How fast you can run is dependent on a LOT of factors, some of which you can work to improve but some of which, unfortunately, you cannot. You have zero control over your age, gender, genetics, and just raw running ability and talent. Depending on how old you are and where you are at in adolescence or adulthood and if you've gone through puberty, your running speed can vary drastically. Studies show that women actually tend to get faster and better at running with age, and most peak in their 30's! Men, however, are fastest just after puberty (late teens into their 20s). Furthermore, your genetics play a big role and effect your tendency to get injured, and just how naturally fast you are. If your parents were natural runners, and your siblings are fast, there is a great chance that you, too, will be fast! However, this isn't always true and you shouldn't feel bad AT ALL if your parents were/are runners and your siblings are fast runners, but you aren't!
There ARE a few things you can work on to become a more efficient runner. First, make sure you have the the right shoes. What kind and style of shoes are best for you varies greatly between runners, and might take some experimenting. Find a specialty running shoe store near you that will size you for the right fit and help find a style that suits you. You can also improve your speed by improving your stride, your footstrike, and your arm swing. For speed, your stride should be lengthened and your footstrike should ideally be a toe to heel footstrike. Your arms should be held at a 90 degree angle and move straight forwards and backwards (not side-to-side across your chest).
Finally, nutrition and training play a huge part into how you're performing. Focus on getting in the right amounts of carbohydrates to fill up your glycogen stores, and proteins and fats too. Make sure you're hydrated, and find a training plan that fits your schedule and helps you attain your racing goals. This'll help you slowly build up strength and endurance, and see positive results come race day!