I think all that you need is to extend the FosUserBundle
If you have already configured you must have at least the User Entity extended.
You can create there the new fields and add this new fields to entity, form, views
You can find more documentation in the FosUser
https://symfony.com/doc/current/bundles/FOSUserBundle/overriding_controllers.html
https://symfony.com/doc/master/bundles/FOSUserBundle/overriding_forms.html
https://symfony.com/doc/master/bundles/FOSUserBundle/overriding_templates.html
Other Tip: You can copy past any controller from vendors friensdofsymfony in your extended and change their behavior
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solved How to create web page profile