Optimize for laptop/desktop (and mobile)

Hello! I am struggling like a maniac making my website for my portfolio. I am editing it on a laptop (Macbook Air '13) and when I look at in on a bigger screen all the blocks have either stretched out or are not fitting as they should. I am struggling so much with fitting all the image blocks on my project pages on desktop/laptop and mobile since they all behave differently. I want all the images stretched out so they fill the width of the browser and fit inside the block. Is there a way to edit it on a laptop yet make it look the same in desktop and mobile? 

My page is johannaboman.com