Have my poor grades really hit my chances of getting into a good(top 15)math grad school in the US?

I study in Asia. I am about to begin my fourth semester. My grades have taken a hit in the past two semesters with 7/10(which reads B- on the transcript) in two analysis courses, of which was quite hard and the other one had me get the highest in the class. My grades in the two algebra courses (linear algebra and group theory) have been both B’s(8/10) thanks to my habit of doing badly in timed exams. I also happened to get a C-(5.5/10) in one of the discrete math classes(it was somewhat hard but the instructor did absolute grading).Currently, my GPA stands at 7.7/10. On the other hand, I was the only freshman in one of my country’s elite math programs aimed at second year students and I was the top student there. My department head seems to have a good opinion of me, terming as someone who can do really well but hasn’t because of personal indiscipline (and he has made that clear to me). Besides, one of the country’s top researchers in his subfield has tentatively said yes to me working under him next summer courtsey department head’s reference.

My concern is my grades would really hurt my chances of going to a good grad school. My questions are:

1. 
   

   How badly would my grades affect my chances of going to a top 15 graduate school in the US? Is there a way I can reduce their effect on my application except for doing way better in the remaining three semesters?

   
   


2. 
   

   Should I rather apply to a Masters in Europe as applying for PhD in the better US universities may be pretentious given my grades?(I really want to go to a good grad school so that I can learn under the best and do really good research)

   
   

(I wish to apply for a PhD in mathematics. I have not identified an interest now but I really like number theory and analysis)