The only way that you can get better is continuing to practice your craft. Whenever you have an idea for a script, try to flesh it out to build up your portfolio. As you continue writing, your work will have a lot more polish and look more professional. Try to set aside some time every day where you can write. Many industry professionals look for multiple scripts in your portfolio. If you only have 1 script, start working on another one so you have more to show off.