header image

Hi Makway. You might try this:
1. Copy header.php from the parent theme to your child theme.
2. Locate the following code section in the middle of the file:

<?php if ( ot_get_option('header-image') == '' ): ?>
<div class="group pad">
	<?php echo alx_site_title(); ?>
	<?php if ( ot_get_option('site-description') != 'off' ): ?><p class="site-description"><?php bloginfo( 'description' ); ?></p><?php endif; ?>
	<?php if ( ot_get_option('header-ads') == 'on' ): ?>
	<div id="header-ads">
		<?php dynamic_sidebar( 'header-ads' ); ?>
	</div><!--/#header-ads-->
	<?php endif; ?>
</div>
<?php endif; ?>

3. Change the first line to this:

<?php if ( ot_get_option('header-image') ): ?>

4. Position and style the elements using css.

The first message is posted using an interpreter. Sorry, I do not know much English. Show in the picture. After modifying it so as in the figure. How to do that red?
Link to picture:
https://yadi.sk/i/mbL9y1FnemEpa

Can you post a link to your actual site? That way we can see the issue. Thanks.

Yes of course. https://kazaksbugra.ru/

I have three days trying to solve this problem.
If you do not modify the file header.php, as you said.
A change file style.css:

#header {
    background-image: url("https://kazaksbugra.ru/wp-content/uploads/2015/02/logo.gif");
    background-repeat: repeat;
}

The picture is inserted into the header. But it turns out the circumcision.

Now Online modified file header.php:
<?php if ( ot_get_option('header-image') ): ?>
as you said.
File style.css unchanged.

I asked my friend to help me with translation, as the online translator cannot do the correct translation and you probably didn’t understand what I wanted to say.
“Thank you very much for your quick reply!
Unfortunately your decision helped me just partially. Probably I didn’t explain properly what I needed. After I made changes in header.php file, the header and the description moved on the top of the web-site and are under the picture at the moment. But I need the header and the description to be on the picture, like a picture is a background image. I can suppose I should make some changes in style.css file, for example to add a background image with specifying the path to the picture. But I cannot get it as the picture becomes trimmed to the size of the original area of the site. Here is the screenshot where you can see what happened after I made changes to header.php file. I marked with red what I want to happen. Thanks a lot!”

ok, here’s another option:
1. Delete the header.php file in your child theme.
2. Copy header.php from your parent theme to your child theme so we have a clean copy.
3. Find the following section in your child theme header.php file:

<?php if ( ot_get_option('header-image') ): ?>
	<a href="<?php echo home_url('/'); ?>" rel="home">
		<img class="site-image" src="<?php echo ot_get_option('header-image'); ?>" alt="<?php get_bloginfo('name'); ?>">
	</a>
<?php endif; ?>

4. Change it to look like this:

<?php if ( ot_get_option('header-image') ): ?>
<div class="mydiv">
	<?php echo alx_site_title(); ?>
	<?php if ( ot_get_option('site-description') != 'off' ): ?><p class="site-description"><?php bloginfo( 'description' ); ?></p><?php endif; ?>
	<a href="<?php echo home_url('/'); ?>" rel="home">
		<img class="site-image" src="<?php echo ot_get_option('header-image'); ?>" alt="<?php get_bloginfo('name'); ?>">
	</a>
</div>
<?php endif; ?>

This now says, if we have a header image uploaded, show the site title, site description and the image.

5. Go to Theme Options > Header and upload a Header Image.
6. Remove the #header background css I posted above.
7. Add the following css to your child theme style.css file:

.site-title {
  float: none;
  position: absolute;
  top: 50px;
  left: 50px;
}
.site-description {
  float: none;
  position: absolute;
  top: 50px;
  left: 150px;
  font-weight: 700;
}
.site-image {
  display: block;
}

Let me know how that works.

Thank you very much for your help and advices!
I based your code from style.css file and made some modifications in order to get what I needed.

It works!