What’s the link to your site again?
Have you uploaded your logo to your media page yet? If so, do you have a link to that as well so I can take a look?
You can change the logo size in the functions file by looking for this code –
//* Add support for custom header
add_theme_support( 'custom-header', array(
'flex-height' => true,
'width' => 300,
'height' => 60,
'header-selector' => '.site-title a',
'header-text' => false,
) );
…and then changing it to match the exact size of the image you want to upload. The 300 x 60 is just a default size, you can still change this if you need to. Let me know if you have those links so I can see how the image is supposed to look.
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