Enfold Flat Business Demo – Image sizes

Hi guys,
I love using the enfold flat business demo to individualize my own website.
I just cant seem to figure out the optimum image sizes.

Instead of the first picture (the blue one) I used my own image (transparent) with a color-section . If I understood the code correct, its supposed to be 1500×430 as listed in the editor.
It seems like every picture (as stated in the editor) is no more than 1500px width, but what about hd?1920px? I don’t want large desktops to see white edges instead of a whole picture.
If I upload a picture with 1920x1280px (I selected “original size”; the initial/”original-orignial” size before using a picture-size-compressor was 5765px x 3843), the 1920×1280 picture doesn’t look good, because my figure from the picture is totally zoomed in on e.g. you can only see my face instead of my whole upper body.
Can you help me?

Thanks in advance
Laura