Here is my advice. Do not let a letter grade determine what you can or cannot do. Just because you cannot achieve mastery in a class within 15 weeks doesn't mean you're not good at it. Everyone learns at a different pace, you just need to find what works for you. Get involved on campus as early as possible. The longer you wait, the harder it becomes to start getting involved, and then you may have regrets in the end. Meet as many people as possible.