Those grading systems aren't in use in the USA, and the UK and Europe have unnecessarily complex regulations and requirements that wouldn't be tolerated in the US. If you had those grades in the US, it would not be an impediment in the current hiring environment, nor would it impede you fro learning to fly. The hardest part of learning to fly is paying for it.

Traditionally, (the current hiring environment is anything but traditional), adademics have mattered. Many employers will ask about your grades, not just at university, but going back to secondary and sometimes even primary education. Those do follow you.

Not everyone is adept at every subject, and generally in technical fields or something like aviation, math and science is more applicable. Good communication skills and a good grasp of English, however, is important to understanding the vast amount of material a pilot is expected to read and absorb, and it's crucial to communication. If it's a weak area, work on strengthening it. This doesn't mean that it's critical that you understand the finer points of Shakespeare, Watership Down, or The Hobbit (though all are good things), but it does mean the ability to read, understand, and communicate. Proper grammar, a good vocabulary, excellent reading comprehension, and the ability to get your point accross, as well as effectively listen, are all critical elements of learning to fly, and working with others in and our of the cockpit. In nearly all environments, you will be judged by your language, whether in aviation or anywhere else. It's a very basic skill, and if it's a weak area, work to make it stronger.

Clearly this isn't an intelligence issue; it's more related to the amount of effort you'll have to expend. It's safe to say that a great many of us were never rocket scientists. Don't lose heart if you're not, or if you don't get perfect grades; development in life is about more than academics. Scores in school have nothing to do with flying an airplane, but the are markers by which employers and others may assess you, so it's worthwhile to score as well as you can.

I haven't counted recently, but I think at this point in my career I've had the opprotunity to fly something like 90 different types of aircraft, including a few unique ones, doing a lot of things in aviation, and I consider myself very fortunate. I come from a very humble background (extreme poverty) and was never an academic. Just remember as you travel throiugh life: you determine your trajectory, not your environment, and act accordingly.