World Quant University (google it) could be a good place to start. Very structured and professinal courses (Free of charge and all online)

Most of the free course in internet lack of structure. Booring stuff and waste of time. ofcourse you will be needed read somes good books. and practice.

It was from there that my learning had began seriously.

I will add the following thing: So already to start learn everything on your own even on the internet according to your preferences.

Then and this is the most important part, you find solutions for problems that you will have to identify in your current company, this will make you practice with a lot of flexibility. When you feel strong enough, go outside and fly higher.