Can bad students be good scientists? I recently moved from an undeveloped country to Europe, and I am currently a PhD student.

In my hometown, the education system is very bad, and almost everyone with some patience can get any degree. However, things do not work like this in Europe.

I have always been a bad student, and I suck at exams (both written and oral). Although I am capable of presenting my own work in an understandable fashion, when it comes to study on some topic -- that is not very related to my field of study, and learn that topic thoroughly, I fail. 

Unlike the education system in my country, here, the tolerance for mediocre mistakes is close to zero. And I do make mistakes very often given limited time to evaluate my own statements/claims/proofs. My exam paper is always a mess compared to my technical reports. Because I get to write the report over on over again with an access to every term, definition, and counterexample.

Back in my country, I was the one-eyed king in the land of blind. Extraordinary researcher, and very good student. Here, everyone has both eyes with eagle vision. My research skills obviously do not shine, and if you consider my studentship, I am just a dead duck.

I do love to conduct research, and not only looking at its butt when it walks by. However, I am pretty doubtful if I can be a good scientist given my current achievements in the courses I take.

Should I go with the philosophy 


  a fault confessed is half 


or should I go with 


  finish what you have started


based on your experiences?
I think most would probably agree that there are cases where someone is a poor student but has the potential to be a good scientists -- because what defines a good/poor student is mostly the ability to be effective in exams (i.e., most importantly to be able to learn and reproduce known material) whereas the skills necessary to be a good scientist are different.

That said, it is clearly the case that the two skill sets are highly correlated. There is a perception in the public eye that the best scientists are mavericks who are able to think outside the box and swim against the scientific consensus to find the things that nobody else sees. But in reality, that is probably a glorification and even those rare insights like quantum theory or the theory of relativity can only be found by those with profound and deep understanding of the existing knowledge, and the ability to synthesize knowledge into something new that those who have not paid the same level of attention to the details of the field can not.

As a consequence, what I read from your description in the question is that you may have the skills to be a good scientist, but that you lack the knowledge and maybe diligence to compete with your peers. That's not your fault, of course, but it's an insight that you may want to keep in mind when thinking about your future. Knowledge is, after all, something that you can catch up with if, for example,you are willing to take some time off from other responsibilities and focus on learning the basics at a more profound level than you had the opportunity to do in the past.