Problem upgrading from Php5.5 to Php7

The image is distorted. It did not work.

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? Yes I made the customizer cut / paste, it works correctly.
? Contact-info (contact page, footer contact) phone logo hover-effect possible?

child-theme style css,
I did an export / import before I started, then I did copy / paste. For the test, I changed the code and it did not work. Do I need to do “Customizer Export / Import” again?

Contact-info (contact page, footer contact) phone logo hover-effect possible?

Since you can’t click the icon itself, it’s not really useful to have a hover effect on it. With this your users would think you can click it. But if you really want it, here’s the code.

.meteorite-contact-info .contact-phone:hover i {
  color: #444;
}

I did an export / import before I started, then I did copy / paste. For the test, I changed the code and it did not work. Do I need to do “Customizer Export / Import” again?

The export/import is only for switching themes. If you switch to a new theme you have to make all the Customizer settings again. Since it was only a child theme you could export the settings and then import them once. Then all the Customizer settings are the same as they were with the old theme.
After that you can deactivate the plugin again. If you want you can copy the code from the Customizer > Additional CSS and paste it into the child theme. If you did that, you should remove it from the Customizer. Otherwise you would have the same code active twice. If you don’t remove it from the Customizer it doesn’t have any effect if you change it in the child themes style.css because it is still in the Customizer.

Furthermore you should clear the cache of W3 Total Cache after changing anything.

I re-enabled the W3 Total Cache, changed the settings, works. I am working on php7.1, I did not fix php 7.2 problem.

I cleaned the cache.
children theme style.css,

# main-nav> ul> li> a {
font size: 16px;
}
I change the font size, but it does not change, it does not work.

? Original Theme / Child Theme; Are the Customizer Panel codes affected by theme updates?

What I want to say is that both the logo and the number are clicked like a topbar phone.

# main-nav> ul> li> a {
font size: 16px;
}
I change the font size, but it does not change, it does not work.

I can’t find that in your style.css of the child theme.

Furthermore you have to remove the whitespace between the # and the CSS ID main-nav. The correct code should be

#main-nav> ul> li> a {
  font size: 16px;
}

Original Theme / Child Theme; Are the Customizer Panel codes affected by theme updates?

No, the settings are not affected.

What I want to say is that both the logo and the number are clicked like a topbar phone.

Please remove your old JS code from the my-custom-functions.js file and use this JS code instead.

jQuery(function($) {
  if ( $('.meteorite-contact-info').length ) {
  	$(this).find('.contact-phone').html('<span><a href="tel:+9005423141341"><i class="fa fa-phone"></i></a></span><a href="tel:+9005423141341">0 542 314 13 41</a>');
  }
})

Is this what you want?

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Works in the customizer, the child does not work in the theme.

What is the difference between keeping the CSS codes in the customizer panel and the child theme? both are not affected in the update. Is it only for php code?

What is the difference between keeping the CSS codes in the customizer panel and the child theme? both are not affected in the update. Is it only for php code?

The style.css is linked as a stylesheet in the html header. If you put your CSS inside of the Customizer it will be outputted as inline CSS in the header.
Since you can use the Customizer if you’re logged in and don’t have to connect via ftp (for example not that easy from a smartphone) it’s easier to handle.
All in all it might be better to have it inside of a file if you don’t need to change the code often and can handle using a ftp.

On your website you say that you know WordPress and HTML / CSS. You might want to become familiar with the web developer tools of your browser. There you can take a look at the CSS of a page and can look whether it’s coming from a file (and even the file line) or from inline code. You can see which rule is active and how you can overwrite it on your own.

Works in the customizer, the child does not work in the theme.

There is a Customizer setting to change the menu item font size. This outputs the CSS as inline CSS too.
Inline CSS has a higher weight than CSS inside of a file. That is why your code doesn’t work inside of the file (it has less weight) but works inside of the Customizer, because there it is inline too and is outputted later than the Customizer setting CSS from the theme.

After all since there is a setting for what you do, you should use that. It’s located under Customizer > Fonts > Typography > Menu items.

As far as I understand, it is more convenient to transfer all file codes of style.css back to the customizer because of its ease of use. Is it correct?

Which codes should I use in my-custom-functions.php? What’s the difference from functions.php?

As far as I understand, it is more convenient to transfer all file codes of style.css back to the customizer because of its ease of use. Is it correct?</blockquote

Use what is more confortable for you.

If you put the CSS code into the Customizer again you still need to have the comments on top of the style.css.

Which codes should I use in my-custom-functions.php? What’s the difference from functions.php?

Please take a look at the WordPress template hierarchy to see what the files are doing. Furthermore there is no my-custom-functions.php. What you mean is the JS file. It’s Javascript. Please read on your own what’s the difference between Javascript and PHP.

As far as I understand, I need to delete some high-weight codes (settings that can be generated from the Customizer panel), such as Fonts> Typography> in the Child Theme style.css file. Because they are ineffective. How should the comments be? Is comment required for deletion?

Regarding the speed and performance of the site, is it better to have the CSS codes in Meteorite Children’s Theme or Customize?

As far as I understand, I need to delete some high-weight codes (settings that can be generated from the Customizer panel), such as Fonts> Typography> in the Child Theme style.css file. Because they are ineffective.

If there is a setting in the Customizer, the theme will definitely output the code. If you overwrite this with your own CSS then, the code is doubled. In case you do that once it will not really affect your site. But all in all it’s not useful do double your code. So you should really take a look which options are provided by Meteorite in the Customizer and use them first.

How should the comments be?

The comment I meant is the default style.css comment header you must have in every style.css of a theme. At the developer WordPress page you can see that comment. That is needed by every theme/child theme.

Is comment required for deletion?

If you move your CSS to the Customizer again you have to keep the CSS comment with the theme information at the top. It’s just like before where you didn’t have any CSS inside of it. There still was the comment.

Regarding the speed and performance of the site, is it better to have the CSS codes in Meteorite Children’s Theme or Customize?

In my opinon this really depends on the size of your code. If you have not many additional CSS rules you can have it in the Customizer. If you’re changing much and the number of your own CSS rules is about of hundreds it might be faster to have them inside of the new file. Nonetheless you might not even notice the speed difference if you use a minification and caching plugin.