[Theme: Sketch] Logo Issues

Hi All, a total wordpress newbie and little/no coding experience – just wondering if someone can give me some help on a page i am doing?

http://www.lothianfirewood.co.uk is the site.

So on the desktop version everything seems ok but when you look at it on a mobile the logo is tiny, can anyone tell me what i can do to fix that?

Also, is there a way to remove that grey line at the top?

Thanks in advance for any help!