Larisa,
As I mentioned to you, you may need to duplicate the security roles and task for the users in question, before you attempt to make any changes.
To duplicate a security role, go to Administration > Setup > System > Security Roles. You will then select the current security role assigned to the users and click the copy button, then enter the new security role you would like to create for them.
Once you duplicate the security role, go to Administration > Setup > System > Security Tasks. You will then select the security task currently assigned to the user and click Copy to duplicate the task, in this case, CARD_0301*. You can now select the duplicated security task and remove access to the Vendor Maintenance security operation.
You will then go back to the security role and unmark the CARD_0301* security task and mark the newly created security task. This should take care of business.
PS. My wife is from Moscow, so I can pretty much identify any Russian name :-), nothing to do with your English by the way.