Hi there @tuanphan!
I need help with the same thing. I either need the entire page to be locked so it cannot change for mobile OR I need the just the section that I've screenshotted below to remain the same for desktop/mobile. When it is stacked it doesn't make sense. I wish I could make it 1 image but they need to be linkable.
https://khaki-potato-c53d.squarespace.com/home
Thank you SO much.