Cannot modify header information.... How to fix?

Question

PHP

After the transfer of the site duplicator'om does not start up in the admin panel.
Warning: Cannot modify header information - headers already sent by, etc.
Resaved files in utf-8 encoding without bom, did not help.
Page with errors - fotografnavypisku.ru/wp-login.php
What is the reason for the errors?
A piece of code from functions.php. The error points to line 387 - header

if ( function_exists( '__' ) ) {
      trigger_error( sprintf( __( 'The called constructor method for %1$s is <strong>deprecated</strong> since version %2$s! Use %3$s instead.' ), $class, $version, '<pre>__construct()</pre>' ) );
    } else {

Answer 1

You can not give headers if you started to give the body of the page

Answer 2

Good afternoon! I have the same error on the line
trigger_error( sprintf( __( '%1$s was called incorrectly. %2$s %3$s' ), ​​$function, $message, $version ) );
dm dm tell me, please, what did you change?