Urgent need for help!

I am still a bit new to unbounce, but have made some landing pages so far.

However, in the edit page the ‘width’ doesn’t seem to be right? I layout everything to fit in those to border lines on the side. However when I save/publish and preview, the pictures that are in the background stretch over the whole screen, way more wide than the outlines in the edit page. The effect is that pictures that I have put as backgrounds for certain sections, get stretched out, causing weird cuts (someones head high in the picture gets cut off and also texts with titles change position in the photo).

Does anyone know why this happens and how I can make the preview look exactly the same as the edit page??

Thanks!