SVG Logo in Header too big, Chicago Pro Theme

Hi, I´m using the Chicago Pro Theme and would like to use an svg graphic as logo. Already installed the svg support plugin and uploaded a svg file. When selecting that svg file as customn logo it is displayed. But it´s way to high/large. Question: can I edit a specific file to add a class for the logo imgage? Which file is to be edited? I can put a copy of that file in my child theme? Kind regards in advance Alex