Logo (header) quality problem

Hi there,

maybe someone can help me.

I have the problem that the logo that I am using in the header (via Theme Options -->Website-Information) is always reduced in quality no matter what I try.
Even if I am uploading a logo in the exact size the quality becomes reduced.

URL: http://doris-weber-personaltraining.de

Thanks in advance

I changed the logo a bit and eliminated the narrow font, now it is acceptable, but would have loved to use the proper oneā€¦
maybe someone can point out how to stop the theme from changing the image.