The main reason the fire doesn't work is the lighting of everything else, to be honest!
If you grab any photo of fire, even during the daytime, and turn it grayscale --

you'll see that the fire is the brightest thing in the image. In a grayscale image, it's going to be defined by the shading around it.
I printed out the image so I could kinda show you what I mean (on the left):

this is really rough shading without thinking about texture or anything, but just adding dark shadows without changing much about the fire, it suddenly looks, well, like a fire! You have to make the shadows of your image very dark in order to make the light parts look bright.
As for the bit on the right, there's some notes about drawing an environment and hiding the horizon line, and also really rough anatomy tweaks -- I tried doing this pose myself, and discovered that having your knees spread that far apart while kneeling is, uh, really uncomfortable. It felt more natural to be closer to this:

with one knee sort of pointed right at the camera if the other was going to be pointed away.
In general, I think the biggest thing I'd advise as crit is to look up what stuff looks like! Even if you're not going to Reference A Photo Exactly, it can help your brain a lot to double-check and make sure you know what something looks like. Strike your characters' poses in the mirror real quick to make sure they're comfortable. Google "campfire" just to see what it looks like. Google "forest." Google some kinds of trees! Not assuming that you know what stuff looks like and taking a look at it before you try to draw it, even for simple stuff, is a really good habit to get into!