Short answer: Yes… and No.
Long answer: If you want to study math at TUM, then sir/ma’am, you are already a genius. Your decision to study math is so brilliant, so exceptional, there is no question that your ingenuity is limitless.
All “jokes” aside, no. Definitely not. The answer to this question should be split into two parts, though.
What are the requirements to be eligible to study math at TUM? That is which people are accepted to the university. I’ll make it short, it’s not like MIT, Harvard, Cambridge or any of those notably reputable universities. You don’t have to be another Einstein to enter TUM. You just don’t. You don’t even have to be good at addition.
By some quick algebra, you will see that your grades do not have to be outstanding. To do so, we’ll make use of the Bavarian Modified Formula.
We now have the possibility to e.g. take a look at the US grading system. Due to the German TUM website, you are admitted directly with a German grade of 2.2 overall and a 2 in math. Converting that to the USA using the above formula gives us that a GPA of 3.2 and a B in math suffices. A GPA of 3.2 is definitely doable, TUM does not require you to be some genius having a 4.0 GPA (whether those people are really all geniuses is another question to be discussed). And in fact, you do not even absolutely need 3.2. If your math grade is better than a B, then your GPA can be lower.
Also, note that with weaker grades you still have the opportunity to participate in a selection interview. That interview is nothing to fear. Katharina Schaar explained at the Infocafé that you can choose any mathematical topic you are fond of. You can prepare that topic at home and then talk about it. The main purpose of the interview, in fact, serves as a counseling interview: Are you ready to enter the university? Do you know what you are doing?
Hence, perhaps the question at hand is not to enter TUM but to stay at TUM. Does one have to be blessed to pass the classes? Famously, in most math classes not even half of the students reach the end.
Even for that, though, I believe the answer is no. You again do not have to be another Einstein. A friend of mine who has recently acquired his MSc. in math at TUM revealed that in reality, most people (of his year) did not fail but rather decided that math was not right for them. These people changed their course of study voluntarily – not by force! For more on that refer to Terrence Tao’s response to the question “Does one have to be a genius to do maths?”.
Math might not be easy as pie (or π) but neither is there a devil at work. Let’s see whether my opinion changes about that throughout my studies…