Still life 4: I am stuck

At the end I didn't find the solution. I have understood  shapes and light but I haven't dipicted it. Next time I will do more thumbnails. I have use white colour because it was totally imposible to show differents values with my sticks.I have only one of it. I think there is another way to paint this complex form. I have tryed to transform into simple structure but I notice i don't have enough technique. It will be a new challenge. I want to paint these roses well. I going to do it.