center and resize header and replace description

Hi, thank you for such a simple to use theme. I have spent the better part of the day trying out themes for a client only to find they were not as ready to go as described.

This theme is gorgeous and my client likes it already. However, she wants the header “logo” to take up about 50% of the width and about 75% of the space right in the middle of the header area. I have not made her a custom logo because I need to know the exact dimensions of the finishes image. however, the header background does not matter as the logo will have some transparency.

I have tried multiple CSS codes in Simple Custom CSS both found up to ten pages in on this forum and from other themes I have edited for other clients and only managed to make the header slip off the left side of the screen halfway.

Is there a simple CSS code I can use with simple scripts to enlarge and center the header logo and remove the visibility of the description? Or shall I edit the theme as explained in the other forum thread and simply upload her custom logo as the background with an invisible header logo and description?

Thank you for helping, her website is amiesugat.com