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

I'm looking for the same solution... It absolutely baffles me that Squarespace has no responsiveness features outside of a generic desktop and phone editor. It's 2024, there are so many devices y'all!! Very frustrating.