Header Image / Site Logo without Jetpack

Hi,

i started using the Sela Theme, but when i put an image as Header, it doesn’t scale properly on mobile devices.

now i read that when i use the “site logo” feature it would work, so i installed jetpack (had to deactivate all other plugins) and the site logo feature is exactly what i was looking for.

but jetpack doesn’t work with my installation because it collides with other plugins, slows down my page really bad and i don’t need any other function from it.

so istn’t there any other css possibility for an responsive header image?

Thank you for this nice Theme and the great support