Metric, great that you're getting back into drawing. Lots of people take breaks from art then come back stronger than ever.
Blackberries are wonderful objects to draw, full of shape, texture and values.
My initial thought on seeing this is that your drawing skills are good in terms of creating the shape that is berries and branches. You need to concentrate on values in this drawing. I don't see a strong light source. Yes, you have highlights on some of the globules of the berries, but not others and there is no shading on the branches or thorns that reflect where the light is coming from.
I think you could also go a lot deeper in the shading to indicate the roundness of the individual globules that make up the berry. I'd also suggest that you buy some good quality drawing paper 70 or 90 lb, a kneaded eraser is useful too. With copy paper, its difficult to get many layers and you often run out of tooth before you're finished your drawing.
You're heading in the right direction, just a few adjustments in this one and you're home free.