Freshman courses are very easy, if you messed up them you will need to really hunker down for the rest of college.
Harvard gets 1000s of apps from people with 4.0 GPA. You can calculate your GPA if you get straight As from now on. It will not be 4.0 for sure. Have you tried taking LSAT? Median LSAT at Harvard is 175. The question is if you will be able to do similarly. But being black is a huge plus though, and may mitigate GPA or LSAT. Harvard is a really long shot though, espiially if you started your college with Ds and Cs...