I like this piece. At first glance, its well-drawn, constructionally dynamic, and thematically clear.
The strongest aspect is the color, especially in the shadows. You moved from warm colors in the highlights to cool colors in the shade making the forms really pop. I can't stress this enough; most digital works omit this technique. Other than that, Toothless and Hiccup's physiology are pitch perfect. All of the piece's elements lead the eye to other points of interest.
One minor problem I have with the work is the water. Water is usually drawn with either reflectivity, transparency, or a healthy combination of both. This has neither making the water look opaque and milky. I would suggest drawing the water to show the stream's floor or the surrounding objects near the bottom third of the composition. I could go on about how there isn't enough clutter for my taste but that notion is silenced by how beautiful this is. Fine job.
Thank you Hmmm Krita can actually be a bit confusing at the beginning. Even I had some trouble, and I've used quite a few programs, including Photoshop. If you have a drawing tablet, I would suggest a program called MyPaint [link] . Its free, and pretty simple to use, but its powerful. Its starting to gain lots of new complex features that you can use in time, but its user friendly enough to use right away, and I believe there are several starter tutorials on youtube. I would never have a computer without it It has layers and a nice color picker, and some wonderful brushes. The only major issue is it doesn't work so well if you don't have a tablet Theres lots of other great free and cheap programs out there though, so I'm sure you'll find the right one for you n_n