That's a huge question, so I'll do my best to do it justice. 

Can you please tell me what type of cases will I face in the interview and more about their structure. 

Any case. From any industry. Typically, it's going to be candidate led. 

For example, in market sizing questions, do they provide you with the data? 

They almost never provide you with the data (regardless of the firm). You almost always need to come up with assumptions. It's part of what they're testing. Typically, they might tell you the population or something like that.

Also, in other types of cases, are there questions and you have to solve them? Please tell me more about their interviewing form and how to ace it. 

Sharing a few example cases that are based on real interviews, with suggested answer:

• https://www.preplounge.com/en/management-consulting-cases/interviewer-led-mckinsey-style/intermediate/mbb-second-round-codewave-employee-turnover-challenge-304
• https://www.preplounge.com/en/management-consulting-cases/candidate-led-usual-style/advanced/mbb-first-round-soy-technologies-303
• https://www.preplounge.com/en/management-consulting-cases/interviewer-led-mckinsey-style/intermediate/element-mobile-expands-into-refurbished-phones-mbb-2nd-round-302

Best,
Cristian
 

They apply the usual case method interview. In this case they may provide data or not, depends on the interviewer. Yes, they'll give you problems to solve and ask questions within the case.

The way to prepare is just like you would prepare for any other case interview.