Danke, ich machte es, aber vergebens

Any kind of help will be much appreciated. 

 "header" field set to single image  - where to do it?

<?php namespace ProcessWire;

// basic-page.php template file 

// Primary content is the page's body copy
$content = $page->body; 

// If the page has children, then render navigation to them under the body.
// See the _func.php for the renderNav example function.
if($page->hasChildren) {
    $content .= renderNav($page->children);
}

// if the rootParent (section) page has more than 1 child, then render 
// section navigation in the sidebar (see _func.php for renderNavTree).
if($page->rootParent->hasChildren > 1) {
    $sidebar = renderNavTree($page->rootParent, 3); 
    // make any sidebar text appear after navigation
    $sidebar .= $page->sidebar; 
}

result :

Internal Server Error

The server encountered an internal error or misconfiguration and was unable to complete your request.

Error has been logged.

should i insert this code every timt?    I thought it's done automatically

ok! thanks!!

how to change structure?   Russian  must be ru/search instead of  en/search

I did that but  Russian instead of  Italian

To use Italian as your default language on the frontend, and considering your want "example.com/" to open in Italian and "example.com/en/" to change to English, do the following:

1. As this is a new installation, and you have no real data yet, delete all languages but the default one, of course. 
2. Change the default language title to Italiano
3. Upload Italian translation files to it
4. Create a new language, name "en", title "English"
5. Edit the homepage and set the "en" language as active and the url as  "en". 

Note: your current server locale setting isn’t working as expected with the UTF-8 charset and may cause minor issues. Your current locale setting is “en_EN.UTF-8”. Please translate the “C” locale setting for each language to the compatible locale in /wire/modules/LanguageSupport/LanguageSupport.module:
• English
• rus

this appears again & again despite i did translate the “C” locale setting for each language  

here why can't i see Russian?

is there something of the kind in your Initial PWBRecipes ?

would be so nice if there was an assembly of ProcessWire  with other languages as default, because it's really complicated! 

i'll try to do as described here, thanks a lot!

or what video to watch may be?

fresh 

SORRY 

https://processwire.com/docs/multi-language-support/   is so big, i read it but just went crazy

can you tell me just briefly what to do after

1. First of all import the language pack. As you have already done I guess.
2. Second to that change labels/titles. As you have done already as well.
3. Third and last part log out and log in again. 

 language pack intstalled  labels changed 

i want that the default  page example.com be in Russian instead of Eng

SORRY I MEAN NOT THE interface but the whole site

how to change the default language in processwire cms

from Eng  to Ru