anyone studying in EBS?

EBS in Germany has a much better reputation than EBS in London. What is WHU? :P
Mannheim and LMU have the best reputation.
However, St. Gallen > all in the German realm.

About St. Gallen: it is definitly among the best Universities in Germany/Switzerland (with Mannheim, WHU, LMU, Goetheuni/Frankfurt) but nowdays I wouldn't say it is the number one anymore as they used to be better in the past then they are now.

I heard that most of bankers of Frankfurt are from EBS.

You heared wrong.

I heard this from a banker of Frankfurt. You are?

Also working in Frankfurt. EBS doesn't even produce enough graduates to field "most bankers". Its simple maths.

Ok then You're right

I guess than grades are more important than the reputation of the school in Germany, right?

Work experience is king. I've seen people from not so great unis with not so great grades get into IB because they got the right kind of and a great amount of work experience.
Networking is also important. Many places will recruit from their networks. Thats how places like EBS place many grads eventho they're not that well regarded.
But yes, reputation doesn't count for much. The place I work doesn't have 2 people coming from the same uni (and nobody from EBS).

Ok thanks, I imagine than German is a compulsory to work in Frankfurt or not? Is there other "financial" city?

Theres IB/PE/VC in Frankfurt, Munich, Dusseldorf and Hamburg mainly. Also some in Berlin. On the IB side, the majority is in Frankfurt with some big banks having offices in Dusseldorf or Munich rather than Frankfurt. Hamburg you're more likely to find IB arms of private banks and small boutiques. PE and VC Munich and Frankfurt make up the bulk, with Munich probably takign the lead in VC.

And concerning the sector of the real estate IB? Do you know it?

No clue. I know that the large real estate firms and asset managers are pretty much allover the place.