I don't see any reason to be rude; for first pixel art drawings, they're pretty good.

I'd say that the best-looking ones here are the flat rocks and the cubes. Their shading is really solid, and they have a good sense of texture despite their limited color palette. The one thing to watch out for is banding, which you can see in the flat rock's upper shading. You can fix that by adding some midtones in between the shading to 'break up' the shading so it doesn't hug the shape as closely.

The rounded cone shaped rock (well, that's what I'm guessing it is) has similar banding problems, and it could also benefit from a little more shading on the bottom to imply its form.

Most of the individual rock piles are fine (except for some pillow shading on the bottom one), but I think their lighting is a little inconsistent.

The shading on the column is well made, but I feel like it should feel more rounded, especially in the rightmost version of it. Try making the middle shades longer than the ones at the ends to give it a better sense of depth.

All in all, this is a good start, and I hope that you keep doing pixel art after this!

This was for this week challenge...but I'm too slow and it will not be finished in time

I think the lighting on the topleft-most rock is off. It looks like it's being hit by two light sources instead of one. You should shade it in a similar manner as the rock that you made below it. The smaller rocks beside it would also be cast in shadow, if the light source is from the top-left.

I also think the pile of rocks isn't very readable. I can't tell if they are supposed to be ontop of each other or not, but if they are, then the ones that are lower in the pile should have more shadows cast upon them and less highlights. (Edit: you fixed the highlight part with your first edit of them)

Still in progress...but I need an advice...

I have problems with the glares in the metal, and the metal it does not seems to metallic...

I have this two solution for now...but...boh...there something that it does not feel right

Nope...I'm not able to do properly the diphering...

After 2 hours of tries, I've not a sigle pixel that seems well positioned...

Colour theory is really not that hard, it's really just about understanding some theoretics behind how colours interact, it's literally just explaining things you already know or observed, but putting it into precise theories. And learning it is 5% watching a youtube vid and 95% just trying stuff out. Plenty of skilled artists, especially pixel artists, switch colours around multiple times for a single piece.

If you wanna go for a monochrome look, you could go for a more blue-ish green for the stalk and a purple for the red bud. If you want to preserve the three colours but want them to synergize more, you should go for a lighter green more towards yellow and a red more towards orange.

Also, if you don't know about hue-shifting (coloured shadows) look that up, it's a major deal in art in general. Pick a colour for your light source (natural light is yellow) and move toward it for brighter parts and away from it for darker parts within the base colour of the object. If you have a gradient tool on your program, that can help you find some hues you like.

I really am an amateur in pixel art...usually my art was edible,I was a baker and a pastry chef and I have done no other jobs in my life.

I started pixel art for fun two moths ago.

It's quarantine time...I was bored and I started whit this piece.

There's still a lot of work to do...

I wanted to do something with nature, trees, flowers, animals and all but i'm no good at making a palette on my own.

Somebody has some palette that could fit well?

That's the other piece I was working on in these weeks, but something's not feel right in the skin...

I'm assuming that this is based on the icon that was recently put on display in the Vatican.

Here's a quick edit that I hope will give an idea on how to address the banding in the face. I also believe that the number of colors used could easily be condensed down. As an example the color I've outlined in red could be gotten rid of and replaced with the color outlined in green which was already being used.

The cloak has a couple instances of banding but otherwise looks great!

I would also make the background as flat as possible, and rework the colors to more reflect the gold leaf of the original icon. This way the Virgin will stand out more.

I hope this helps!

This is the result...if I followed your advices well...

Maybe 18 colors is still too much but when I take off another color the result is worse than earlier.