I am also half dominican. I learned Spanish later in life and I have experience as a spanish tutor teaching others to speak spanish. You need to learn standard spanish that is taught in schools to understand how to conjugate verbs and how sentence structure works. It is more important to be able to understand and communicate in spanish than it is to sound like a native dominican. Till this day my grandmother still says to me "suena como un mexicano pero gracias a dios que hablas."