I'd advise you to attempt to achieve at least Bs in your core subjects (maths, English, sciences), but As or A*s would be preferable. Furthermore, if Dutch is your first language, some medical schools may not accept it as a valid A Level. If you work hard, it may well be possible for you to achieve fantastic A Level grades - AAA is the minimum you'll need at A Level for the vast majority of medical schools. I'd also advise that you attempt to achieve all As at AS in order to prove to medical schools that you are capable of achieving such grades. It's also very important that you research the entry requirements of medical schools before applying and apply to your strengths, e.g. if a medical school places less emphasis upon GCSEs and more emphasis upon AS Levels, you'd be better off applying there than applying to a medical school with a GCSE-heavy application process. But at the moment, focus on trying to achieve higher grades than those you are predicted at GCSE - good GCSEs won't guarantee you a place at medical school, but they'll certainly make your life a lot easier.