Responsive logo height

I've search your forums but didn't see a straightforward solution. I have a logo in my header that is 100x100. When I go to a smaller screen size the logo loses it's proportions and becomes 45px high. How do I make it show the full 100x100 logo on a smaller screen size? https://scifipartyline.com/wp-content/uploads/smush.jpg Or you can go to my website and see it in action for yourself. http://scifipartyline.com Thanks in advance for your answer!