Yes, you can.
According the brain researcher Dr. Lara Boyd, our brain is like plastic. We change the structure of our brain while we are learning. By practicing we can make a new connection between neurons and strengthen it. That means if we work hard, we can become smarter even you are in a old age.
If we decide to do something well and we work hard, practice a lot, then new connections in our brain are created and become strong.
There is a conception among people that your intelligence is not improving after puberty. But this is far from the truth. Your brain is like plastic; you can change the structure by repeated practice. That means if you put a lot of effort, you become smarter. That means you can become a kind of person you want to be.