Some time ago, while trying to learn python, I stumbled across coursera.org. Via coursera.org, I found two python courses. They are free to follow, to enroll, and to enjoy.
Since then, I took a refresher course in Linear Algebra, Compiler Design, Algorithms, and Converting from C to C++.
Each course requires about 8 hours per week of concentration. The courses have pdf file handouts and videos.
The difficult part is being able to set at the computer for 8 hours.
I am a senior (age 70+) and I don't want to have a rusty brain.