My main programming languages are APL, D, JavaScript, and Python. I golf in APL and Jelly. I am working on a stack-based code-golf language named MY, the decent Hello World answer is here for the MY programming language: https://codegolf.stackexchange.com/questions/55422/hello-world/127294#127294

I do best golfing other people's code by looking at small syntactical elements, rather than the code as a whole (I probably don't have a clue what your code does if I suggest a golf).

I am the 3rd place winner of the Dyalog 2017 Student Competition (https://www.dyalog.com/student-competition.htm), that was actually pretty fun!