Can two or more people log in to a Magento e-commerce site at the same time? Can one person process sales while another updates products?
You need to enabled Admin Account Sharing option from admin to allowed logged in same user simultaneously.
Go to Admin >> "Stores > Configuration > Advance > Admin > Security" and change value of "Admin Account Sharing" to "Yes".
Second thing - Yes that is also possible one person do sales operations and another will do updates products with same user.
Note : But still as a part of Security Create new user for sales with limited access by using ACL functionality of magento 2 and give access to sales related operations to sales user same way for others.