Please critique & give tips?

I’m horrible at doing any kind of shading/ figuring out how to make it look more realistic. I would love some feedback on how I can accomplish that & what I’m doing right/wrong. Thankyou in advance

I’m horrible at doing any kind of shading/ figuring out how to make it look more realistic. I would love some feedback on how I can accomplish that & what I’m doing right/wrong. Thankyou in advance