[Theme Horse Support Team]

Hi Elena,

Please upload or edit the logo in small size and your logo will be display as small in the header.
If you can not edit then Go to Appearance -> Customize/Theme Options -> Design Options Tab -> Custom CSS paste the following CSS code and Click on save button:

#site-title a img {
    max-width: 200px;
}

Note: Increase/ Decrease above digit value 200px to change the size of the logo.

Thank you!