when i get older will my voice (singing-wise) get deeper/more mature and sound better?

YouTube is a great source for free singing "lessons". Just search whatever you're looking for, and it just might be there. Your voice will deepen as you mature, but your tone quality/breath support/other important aspects of decent singing have to be worked for. Your voice won't magically become amazing when it gets lower. Keep working on your technique and practice a ton! Practice makes perfect. Now would be a great time to begin auditioning, if you wish to do so; it will give you a lot of experience that those who wait won't have. Even if you don't get whatever it is you're auditioning for, remember that you tried your best.

Good luck!

Your still going through puberty and that will not finish till your about 18 or 19. Your larynx is growing longer, wider and thicker right now and as it reaches maturity you will lose your high notes but gain in lower notes and power. The larynx will also drop and become bonier - This will be your adams apple.

Please, please do not listen to wannabe singers and teachers on the web who have no qualifications in laryngeal biomechanics or the Physics of sound. Wait a while and then get a good voice coach who will teach you one on one in their studio. Until they know your muscle size and lung size and palate shape - no one should be advising you.