...
I know a bit how you feel. My grandfather passed on when I was just 10.
I didn't know him that well, but he was still nice. I always liked going over to his house in the countryside and seeing him and my grandma. He had been in the hospital for a while, but I had never known anyone that died before, so I didn't realize how sick he was. When I found out about his death, I completely broke down. I stopped doing my work and needed to get daily counseling from the school counselor/psychiatrist. After a week or so, I was able to start focusing again and got all of my schoolwork back on track.
However, a few months later, my great-grandmother passed away. I knew her less than I knew my grandfather, but it still hit me hard as I remembered when she used to always teach me piano. I didn't have a complete breakdown this time, just went into a state of semi-shock/depression. I kept doing my work, but I stopped acting excited or like I had any energy at all. I wasn't even sad really, just lifeless, not talking to people, not showing emotions, not even playing games. This lasted longer, but eventually went away. After her funeral, my cousins, family and I went to the beach to mourn. I spent the whole time skipping rocks off into the sunset by myself.
I have to say though, I consider myself very lucky. I still have two grandmothers and a grandfather who are healthy and more energetic than most people I know their age. I also have my brother who helped me through these hard times. He wasn't able to grasp the concept of death at the time, and was able to pull me through my depression. He's always been the optimistic one out of the two of us, and I am really thankful to have him. I don't always tell him because we're brothers, we get into fights sometimes. But at the end of the day, we are always glad that we have one another.