1. Weak in English or German Language
The language level of the students will be tested to see whether they would be able to comprehend lectures and pass examinations successfully.
As a student your ability to succeed academically is of high importance to the embassy and hence anything that would hinder your academic progress can be a reason for rejection. For English-medium courses in Germany, If you have a very low score in your IELTS , the visa officer would doubt if you would be able to understand and pass lectures in English and this can lead to your visa denial.
For a German medium course, you need to learn German to a certain level and should be able to speak it to a certain degree. Your interview will be conducted in German Language if your scourse is in German. Not only you should be able to read and understand German, you should be able to speak it as well.