The technical interview was held by a guy with "10 year experience" that had the impression that class coupling refers to the number of arguments in the constructor.
The interview is a rating of how well you know the SOLID (anti)pattern and the questions asked are directly related to that. So if you are not using the SOLID pattern or if you are unfamiliar with it's definition then you will fail that interview.
No actual questions about logic.
No actual questions about the language (c#)
He got confused at some point and asked me if we're talking about c# when i gave a more complex answer about class coupling / inheritence or polymorphism.
Summing up the interview was a bad experience because of the fixed questions, illogical approach of the interviewer and assessing a pattern that i did not use for a long time as the actual interview result even tho i said at the beginning i did not use it for a long time, he even had a paper with ratings about the individual letters of the pattern.
When i got asked what other things i knew he got lost in my answers and did not know basic language features or syntactic sugar.
So yeah learn the solid pattern and you pass the interview, no other knowledge is necessary there apparently.
I would rate the difficulty of this interview as non conforming with the actual role i was supposed to take there.