Your leaves are really nice Marina! Overall you have nice smooth toning! On the tangerine I see a lot of one tone and it would benefit from adding a range of tones. The reflected highlight seems too long and too much of a thin line. Look at the cast shadows again. The shadow on the right looks out of place. Shadows don’t have to be literal, but simply give a suggestion. I would definitely lighten the cast shadows and scale back how much I showed of them. You are almost there!
Your leaves are really nice Marina! Overall you have nice smooth toning! On the tangerine I see a lot of one tone and it would benefit from adding a range of tones. The reflected highlight seems too long and too much of a thin line. Look at the cast shadows again. The shadow on the right looks out of place. Shadows don’t have to be literal, but simply give a suggestion. I would definitely lighten the cast shadows and scale back how much I showed of them. You are almost there!