Thank you so much for your time and feedback! 

And thank you for the example it helped a lot 😄

I think you're clearly on the right track. There are different ways of dealing with grass. Usually, you can pixel individual blades of grass in the foreground and gradually move to large clusters of different colors, representing (and exaggerating) color variations or uneven terrain in real life. I've made a quick and sloppy edit here to get my point across.

It's the wrong canvas size and not the best choice of palette but I hope the idea makes sense, even at a smaller scale. Of course you can add much, much more detail than I have. Especially if you use more colors. But it can also be valuable to simplify a picture to create empty space, letting the mind rest between the important details, like the signs, the river or the trees, which you may want the viewer to linger at. :) 

PS: It's probably stupid of me to offer advice in the middle of a friendly competition. Apologies if that seems daft.

Thank you for the feedback :D 
I applied it (https://pixeljoint.com/pixelart/147504.htm) and also bought a copy of "Learning Pixel Art by Max Hervieux" 

If it is not too much to ask, how would you add texture to make it look like this photo I took (https://www.instagram.com/p/B8oBcIFjOxd/)??

It is had for me to replicate this kind of grass at this scales :P 

Thank you! 

Welcome to PJ, alcon! Good first submission. Since you welcome comments, my suggestion would be to avoid single (orphan) pixels during the early phase when you're learning to do pixel art. It often adds noise without actually having information. A chaotic pattern of single pixels don't look like grass or rocks or sand, they're just... something, or maybe nothing. When you're starting out, it's better to experiment with bigger clusters of pixels, to learn how you can indicate whether the ground is grassy, rocky, uneven, dry, wet, muddy, cracked, whatever. If it's all grass, maybe indicate that some grass is in shadow, while other is in sunlight, or that they're different types, or growing on an uneven surface. Something that is interesting to look at. Good luck