[banner header]

Strange, should be good like that.
Can you show me online sample ? url ?

Sure, check it helpful man ??

https://iuseconomic.pl/

try this

<header id="header">
<a href=“/”><img src="https://www.yourwebsite.com/wp-content/uploads/2015/02/header.jpg" style="display:block;margin-left:auto; margin-right:auto;width:1380px;" alt="header"></a>

and change site title url also :
https://iuseconomic.pl/

to

https://iuseconomic.pl

Uh, it doesn’t work. ??

site title link should be set in wp admin > general settings.
I think right now you have
https://iuseconomic.pl/

change there to
https://iuseconomic.pl

then change is child theme header file the ahref part to this

<header id="header">
<a href=“/”><img src="https://iuseconomic.pl/wp-content/uploads/2015/02/11009441_710754425710425_392152086_o.jpg" style="display:block;margin-left:auto; margin-right:auto;width:1380px;" alt="header"></a>

Hm, i had https://iuseconomic.pl
So that isn’t a point. :/

so when you say it doesnt work, what do you mean, did you notice any change in code after applying change ? Can you post online example after change ?

i see now what happens
will try to find a solution

Great! ??

and this ?

<header id="header">
<a href=“”><img src="https://iuseconomic.pl/wp-content/uploads/2015/02/11009441_710754425710425_392152086_o.jpg" style="display:block;margin-left:auto; margin-right:auto;width:1380px;" alt="header"></a>

Didn’t help. But now nothing add unneeded fragment in adress, and don’t repeat.

@pandorasan
https://disk.yandex.ru/client/disk
I think you need to update the theme

@pandorasan
https://yadi.sk/i/ZJF6vwboeoHeP
I think you need to update the theme