"Complete the entire form"? Indont know what to do.

Im new with apple and im trying my hardest to understand it. I have my account and passwords but when i want to download apps in the appstore it makes me sign up again and THEN makes me complete some other information on the Apple ID. I try to put everything what it actually asking and when i press Next it quickly saids "You did not complete the entire form" i dont know what to do. I honestly try step by step the information asked. Please help. I cant download apps