In Bitrix24 each CRM record can have only one responsible person. Access permissions can be granted to responsible person only or to responsible person & department, so that users of the same department will see each others records.
But how can I add also all e-mails (mainly Contents) , which come fr om this external user ?I
If the user clicks reply on the email (sent to him from Bitrix24) - the answer will automatically be added as task comment. I'm afraid there is no option to force simple emails into the particular task in Bitrix24. You can only send email to Bitrix24 as new task wh ere you will be set as responsible (with the help of special code on your profile page).
is possible in this same task add any comment, which this external user can not receive - any internal comments
You can add calendar events from your colleagues calendar (see this). Tasks calendar is a bit different - in order to have new entries to this calendar - you need to add new tasks - in the task form you can set another user as task creator and choose other users as responsible person - tasks will appear in the responsible person's calendar.
Currently the address field for contacts and companies is not displayed in your Bitrix24. This is a temporary issue connected with Bitrix24 CRM module updates. You can now add company or contact address under Contact details - add new Legal person - Address.
Please note that this issue is temporary & address field will be put back after the updates. We apologize for the inconvenience.