Hide the user info from other companies / Separate multi companies user info access

First of all, you need to select the corresponding company inside the contact information. It should be in [Sale & Purchase] tab and you will find [Company] field in [MISC] session. It is for the records which are created by Admin and having multi companies access right.

Create a new group

Application: Extra Rights

Name: Hide Other Company Contacts

Save

Record Rules --> Add a line --> New

Name: Sales Person Contacts

Model: Contact

Click [Save & Close]

Domain: ['|', ('company_id', 'in', company_ids), ('company_id', '=', False) ]

Users tab: add the user who won't see other companies' users info. 

If the user is created from administrator, you need to pay attention that the administrator can't have company_id attached. Otherwise, the created user won't be able to edit his own record. 

You need to create [FILTER] to hide the administrator. Enable the debug mode. Go to contact and click the bug icon on the top next to notification icon. You will find [FILTER] under User Interface session. In there, you can create a filter to hide the administrator like this domain ("name", "not ilike", "Administrator")

Other useful information for your reference. The details please see the video.
['|',('supplier_rank','=','0'),('supplier_rank','=',False),'|','|','|','|','|','|',('create_uid','=',user.id),('user_id','=',user.id),('user_id','=',False),('create_uid','=',False),('parent_id.user_id','=',user.id),('parent_id.user_id','=',False),('parent_id.create_uid','=',user.id)]

obtain from https://www.youtube.com/watch?v=4Pam0P0qvlI