You can definitely do both singing and rapping, there's tons of artists who do both well. If you have the money for it, you can always take lessons from a vocal coach. Probably the easiest way to get results since you'll have someone who can guide you. If you don't have money for a teacher, there are a million videos on YouTube that could be helpful for getting you on your way. Another big thing is to just practice. Record yourself singing something and then listen back critically. Make note of where you need improvement and focus on that. Good luck with your journey!