Is it OK to have a significant drop in grades when moving from the Middle East to the EU? I did my Bachelor's Degree in physics in the Middle East, graduating with the highest honors and an academic transcript full of A's. I was accepted to pursue my graduate studies in one of the best universities in Germany. I was able to score above the minimum required score to be admitted to the final exams. My performance was awful in the exams, even though I studied very hard.
I try not to compare myself with my colleagues but they are much better than me, or at least I believe this is what my professors might be thinking. Is this something normal because I am studying in a different country now? Or because graduate school is meant to be that hard? Does it get better? Does anyone have any advice to survive graduate school?
Clarifications:

Language was not a problem (the course is taught in English, which I understand perfectly, though it is not my first language)
Due to the pandemic, the teaching was suboptimal, and the material was so dense that I did not have time to prove every equation and apply every concept.
Background: Some time ago, I've been working at a German university as an assistant in electrical engineering, and we had some students from Arab countries.
Generally, they were much better than the Germans in reproducing content they had learned, but had more difficulties than their colleages in applying that knowledge to the problems at hand. And the university valued knowledge application much higher than knowledge reproduction. So they had a hard time adopting to that different learning style.
Coming back to your question:
It might be that from a different cultural/educational background, you're used to a different style of learning than what the German university expects from you.
My best recommendation would be to seek contact to your professors and your colleage students, to find out what the professors expect / what the other students do differently. Try to find some colleages to form a learning group.
Your colleages are surely not brighter than you, they only have better adopted the learning style that the university expects (they grew up in the same educational system where they are studying now). Most probably, they'd have comparable problems when going to a Middle East university.