unfortunately I can’t access my o2 app and not even in website

First register your contract with the phone number.

https://login.o2online.de/signin/XUI/?service=UserRegistration#login/

I did register but still can not see my rechnungen 

I receive this error when I try login in my O2

What are you registered with?

Hi ​@sepidehemadi ,

following up on Bumers questions: Are you entering your login data manually? If so, are you using the same browser for your access to the o2 Community?

If possible, try using a different browser for the contract login. Thanks for the screenshots! Is this message being shown right after you typed in your number and password?

Best regards
Kurt