What should the design layout of the page look like: requirements and standards, are there any?

Question

Design

There is a designer who only knows print design. He delivers his "templates" to me in the form of pictures without the slightest indication of sizes, indents, color codes, nothing at all. You have to do it by eye. After that, they also make claims to me that something does not correspond to something. Unfortunately, this is a personal friend of the customer and they do not want to change it at my request.
The question is - where to find the generally accepted standards of how the layout should look like, given for layout, and poke the nose of this "brilliant designer"?
Language - English or German.

Answer 1

This is not a standard, but rather a set of requirements .