It helps but it’s not necessary. I did not have good grades. This makes certain doors more difficult to open but this is not impossible. If you try hard and are resilient, you can make things go the way you would like them to go. The advice I would give you is not to listen to the people who tell you that you are not bright enough because you will come across lots of them. If you are passionate about it, if you try hard, you probably have everything it takes to do what you are aiming at. Good luck!