Header image and other images not responsive

Hi,

I have the business directory theme, Its all set out on the template so in general set up you just add the image url to add the header image but the problem with this is it takes the size (1140×158… i think?) but normally i would go to the page text and just edit width to 100% but as its not listed anywhere I was wondering if anyone knew what I could change in the css file or php file in file manager?

also having the same problem with one of the search layouts…. it has a small search box on right 35% of screen and a image beside it at 65% of screen I can edit the width of this picture in the settings of the layout selection but when I edit it to 65% on the mobile phones it puts search box above as it should then the image below but again only at 65% of screen width …. any help is appreciated