I succeeded in creating the account creation and account modification form.
I also created a 'business profile' post form (a custom post type) that each logged in user can use to create a custom post conaining their business information.
To prevent the user from entering the same information several times (first when registering a WordPress account and then in the custom post form for creating the business profile) I would like to know if it is possible to retrieve in some fields of the custom post form the name and first name of the author that is to say the name and first name of the logged-in user.
Note: as the values in these fields will be pre-filled, you can also hide them using custom CSS code, so that the user can't make changes to these field values.
I hope this helps and please let me know if you need any further assistance around this.