Very new with responsive design and design in general but picking up knowledge here and there.
I picked up a free template online which has a responsive design (https://html5up.net/future-imperfect). I made a small adjustment to the top of the site to include a full width image (no size restrictions). This looks great on a PC/tablet but on a mobile device it seems to shrink the image. If you resize your browser on the above link you will notice how it adjusts the image accordingly but the image i have (dimensions of approx 1900x 860) doesnt work the same way.
I can provide a link but before doing that can anyone advise the minimal things i could check? i.e. the image must have XYZ class etc or wrapped around a certain div etc?