branches are literally just there so you have a structure to paint a canopy of leaves onto.
its a waste of time shading branches that will be covered in leaves and shadowed.
in fact its counter-productive because what you've done here is made an overall flat shape with a bump giving the impression of a sponge sticker.
branches are too short and stumpy.
increase ur canvas to free ur mind.
loosen ur lines, extend branches out and experiment with curves.
branches get slowly thinner as they extend out.
consider 3d space where some branches come forward (use light colour) while others are behind (use dark).
make several rough iterations and compare which ones look good (use layers if u have them).