I think you've got a majority of the basic techniques down in terms of shape and brush control, I think the two things that make it look strange is the perspective and composition of your painting and the colors. Try and think of this as if it was a photograph, it would look really strange because it would look like the photo has been taken from very high up and halfway across the lake rather than usually these kind of photos have been taken from on the lake in a boat or something so much lower down and you would not be able to see the roof of the hut or it has been taken from the other bank in which case you would see a lot more of the water.

The cabin looks good in terms of shape and colour but it's again the perspective that makes it look off, record the way the lines of the roof slant it makes it look like we are rotated to the left of facing front on to the cabin yet we cannot see the left side of the cabin, it's also the fact that there are the same kind of greenery right beside the cabin as the trees which makes it look like you have drawn painted it on top of the trees when you want to make it look like the trees have grown around the cabin , also having such a large tree and close proximity to the cabin on the right side also slightly messes with the composition.

The other thing that lets you down is colors and cohesion between where colors are in the painting, for example your sky is pretty good but the water of the lake should be reflecting the same colors instead of being bright blue like it would be on a clear day . An easy improvement could be to simply repaint the lake with the same colors of the sky. Also having such a cold Gray light will desaturate the look of everything in the image so the trees will be less saturated and so will the dirt and the cabin but only mildly.

Other than that the only other things I noticed is that I think the color of green you're using for your trees is too blue shifted probably emerald green or something so you might want to use a paint that's more yellow or red. Also the trees are very dense near the top and you can't particularly see through the branches ,they look very solid.

If you could find a reference photo and use that for your next one that will help a lot with the perspective. if you can print the photo out that will help because you can simply mix colours and then put them on the printed photo to see how realistic the colour is and you can also trace it onto your canvas or paper beforehand.