Adjusting your logo size for a better display can be done in two ways, enhancing its appearance and allowing you to make a more attractive website.
To change the logo size:
You can also use a layout tool to further alter the logo size if you are a paid user. To do this, go to the editor, and click on Design. Go to Website Structures - In this tab, click Advanced Structure Options - Here you can find the Header Size field. Adjust it to be bigger or smaller in size from the dropdown, either enlarging the logo size with the header or shrinking it and the header as needed.
You can learn more about it by going to this link: You can also check this article to learn more about the various options of how to display your logo perfectly on your website: https://support.site123.com/website-name-and-logo/displaying-a-perfect-logo-various-options