There are some extension can help you add and update customer data in magento 2. I would like to recommend this extension: Magento 2 Customer Attributes Extension.
Customer Attributes Manager empowers you to manage customer accounts in a much better way
- Create new customer attributes/customer address attributes with ease
- Various Customers input Attribute types
- Add customers information in the registration form
- Information can be displayed and edited easily on Customer Account dashboard
- Manage attribute options and label for each store view
- Admin can set a default value for the attributes
- Allow different input validation for the attributes
- Ability to allow attributes to show on Manage Customer Grid
- Ability to add the attributes to the filter options in Manage Customer Grid
- Ability to set the attributes available on search results in Manage Customer Grid
- Admin can set the sort order while creating the attributes
- Compatible with One Step Checkout extension
- Create new customer attributes with different field types
- Display all custom attributes on customer account dashboard
View details: https://landofcoder.com/magento-2-customer-attributes.html/
