Most of everything I know about landscape painting I've learned from FZDSCHOOL (more specifically the Design Cinema series). The illusion of depth in 2D images is a simple matter of adjusting values (objects closer to the 'camera' are darker, objects farther away are lighter, Feng Zhu talks about this a lot). Scale is a bit trickier as it relies on both perspectivevalues. Perspective altogether is a pretty tricky subject for me so I don't think I'm all that good at creating a true sense of scale in my paintings. Not yet anyway.But the important thing is to remember that at its core everything goes back to light and shadow, and once you have a somewhat decent understanding of those, painting as a whole become a lot easier. If you haven't already, I would recommend watching Sycra's Foundations of Light and Shadow series. He has a series of color tutorials on his channel as well, of which I would recommend Understanding Color and Value and How To Choose Colors That Work However, looking at your deviations I feel like you already have a good understanding of light, shadow and values (probably a better understanding than I do). So if it's only landscapes you're struggling with, FZDSCHOOL is the way to go. I feel like I learned a lot from just seeing how he paints.