Combine several field as a new field
I think there are several ways to go about this, but with your current field setup and familiarity with template you can use the trans functionality in Twig (see https://www.drupal.org/node/2047135).

{% trans %}
  statistics: {{ node.field_max }}/{{ node.field_min }}/{{
node.field_min }}
{% endtrans %}


Other ways of doing things:


hook_entity_extra_field_info()
Display data via views (see nizz0k's answer)
Translate in PHP in the template preprocess function
Create a new field type that stores, min, max, and computes statistics via a Typed Data method.
Similarly to the above, add a typed data data type plugin to calculate statistics.