Hey @tatasarts,
It is hard to see where you may have gone wrong, because of the external image viewer.
But I can see you are using a later version of Blender. Some behaviors may be a little different, exact numbers as in the course will not get the same result. Notably the lack of a Musgrave texture and the color mix nodes have changed, as well as the Principled BSDF.
I also notice you are not using any subsurface…
This can make a difference to the look of the snow.
It also looks like you may have an issue with the leaves, they look like they are using a negative normal/bump.
Try laying out the nodes as you see them on the screen, this helps to identify any missing nodes or connections, and to tweak values based on the video to see what does what.
If you can share your file via dropbox, google drive or similar we can take a closer look.
