Q:

display custom user fields with twig?

I added for users a couple of fields : field_telephonenumber and field_company
how can i display them in user.html.twig or maybe page.html.twig 

A:

You can configure which fields are displayed in the view mode compact:
admin/config/people/accounts/display/compact

Then you can in twig display all fields with
{{ content }}

or single fields with
{{ content.field_example }}

To put a user in a page template you can use Twig Tweak:
{{ drupal_entity('user', 1, 'compact')

The third parameter is the view mode and you can use theme hook suggestions to catch this with your custom user twig to make adjustments of the user fields.

