Always post at original resolution, there's no need to upsize here on the forums!
As for feedback, your lines are a bit thick and the shading makes it feel more embossed than thought out. The trunk is waaayy too thick in comparison to the foliage too, it should be 2 to 3 times as wide and fluffy as it is now!
Look at some pictures of real trees and try to work from that, it'll help oodles to learn how to study and use reference images!