Hello GAEV SRL,
Welcome to the Microsoft community,
I understand you are unable sign into your account as you always get an error message, I totally understand how you feel about this and I sincerely apologize for any inconveniences you must have experienced on this.
To further assist you better, I would like to know;
*If you are experiencing the issue with other Microsoft services,
*If you are experiencing the issue on the web or on the App,
*Which region you are located,
*The type of device you are experiencing the issue on (Windows, Mac, Mobile Android or IOS),
However, kindly try signing into account.microsoft.com to confirm you can sign into your Microsoft account, and also confirm that your Microsoft account is set up for the right region, I will also suggest you try changing your internet connection and disable VPN if you are connected to any.
Best Regards,
Chidimma | Microsoft Community Support Specialist