Curve Fitting

It is wonderful to see how so many things that we learn individually in our mathematics class come together to solve one problem statement

Lets say we have the density of returns of a particular stock. I want to know the mathematical formula that would simulate the graph

In the graph shown above, we have the returns for  AAPL. Now I tried using the Generalized Hyperbolic distribution and fitted it using Maximum Likelihood Estimation. It has done a pretty good job but we want to be more accurate. We will see what else we can do to make it more accurate