Hey!
I've made a bit of a mess on it but i'll explain stuff
First off congrats, it's bold and has a lot of things going on. It also looks pretty good, these are some of my comments:
1. Perspective - make sure you know where your horizon line is [eye line] and keep track of your vanishing points [Vp1, Vp2], its easier to determine how things look in perspective that way. For example, if the two soldiers have the same height then the one that is in the distance shouldn't be "taller" unless he's on higher ground. Normally they'd appear to be at the same level.
2. Focal points [noted A and B] - it's hard to tell what the painting is about. The most important part seems to be the bunker but the tree is so "important" in the image that it "fights" the bunker so it's hard to say what the image is actually about or what i'm supposed to look at. Try to make your decision clear and show it to the viewer.
3. Values - Some of the values are still too dark. Remember atmospheric perspective and how things fade in the distance. You did it well on the mountains but again, the left tree and some other areas were too dark.
4. Color - I think the image altogether could use a bit more color variation. Everything plays around the same tones, in some places it's hard to tell different materials apart from eachother, etc. The soldiers' colors could also have a slightly different tint, guy in the distance is barely visible now.
To check your values, make a new layer on top of everything, fill it with black and set it to saturation. You can tick it on and off to keep checking your values without being distracted by color.
Hope this helps,
good luck!