Is it normal to think i won't be successful?

I come from a well-off family from a poor country and study molecular medicine in Germany. I went to the best school in my home country but still educational standards there are lower than in Germany so I got a higher note than I would in Germany. This way I ended up in molecular medicine without 100% deserving to, but on the other hand my school was teaching German material for the German final exams and it was so bad everyone survived only with expensive private lessons and I felt mentally abused by the whole system. In school I was not the best in the class and in university everyone seems to have the perfect routine. They manage to always be prepared for the next lecture while I manage to learn a third of the material for the same time. Everyone around me is very responsible and mentally stable and eager to achieve more, but I am introverted and depressed and can't even do my studying on time. I don't believe someone would take me seriously and I don't think I would get/deserve a well paying job, unless the only thing I think about in the next 10 years is hard work without any right to complain. Is it normal to think I won't be successful or are my views far from reality? How is it possible that my fellow students achieve so much but still have time for themselves?