Suppose you have two partner folders (and you want the site / parnter section to include only users from the partner group, let's say the group ID is 201) and there is a / employees folder and you want only employees to enter (suppose Group ID 202).
Create the following entries in the .access.php file:
$PERM["partner"]["*"]="D"; $PERM["partner"]["201"]="R"; $PERM["employees"]["*"]="D"; $PERM["employees"]["202"]="R";
Somewhere else it is in the admin interface, but I don’t really use Bitrix GUI, so I don’t remember.
And one more thing. Do not remove access to the admin account, even if it has the rights to all folders. Just limit the use of this account to employees so that it is used only for rare important operations such as updating the kernel.