I really struggled with a math class after I transferred to university. I was doing really well on the homeworks, but so was everybody else. I typically scored near the average on the midterms and went to every single discussion section. There was even a discussion section that was poorly attended because everybody was busy studying for a midterm in the co-requisite class, but I really wanted access to all review material. Despite all my efforts, I earned a D-. I was so so crushed. I wanted to cry. I thought scoring near the average and having (almost) perfect homework scores would at least get me a C, but I bombed the final pretty spectacularly. It’s hard at the university level. No professor is the same as another. I had one that stated he doesn’t care about grades and claimed that he’s never given a student an F grade - 80% get a B- or better. Another professor (that I had unfortunately) likes to curve his class in a way that meant more F’s than A’s - 35% of the class typically fails. One bad grade should not totally define you. I think attempting to re-take the class will look good on your part. It shows you didn’t just give up and accept the bad grade; you want to do better.