Header image/slider problem, help!

Hi,

I’m new to WordPress and trying to build my first sites. I’m using a child theme made out of the original twentyeleven theme. I added a metaslider above my menu bar, no problem with that. But then i tried to add a header image (logo) above the metaslider and this happened:

https://goo.gl/photos/8wTuJp4dzhkidGuV7

The slider was apparently resized according to the header image. I need the slider to be as wide as my menu bar is and the image above the slider to be in the upper left corner, around 50% of the length of the menu bar.

Any suggestion how to accomplish this?