I’ve been toying with Juce for only 2 weeks now, but I do have 20+ years of C/C++ under my belt. If you get stuck on issues like the example you gave, your problem is a priori C++. Any good C++ programmer/tutor can help you with this example.
My advice: set aside some time to really learn and understand C first and then tackle Juce. Getting to know Juce once you have C++ is pretty straightforward (to me at least) but still takes time (for me at least )… You’re trying to deal with 2 problems at the same time; fix the fundamental one first. And set your expectations: becoming proficient in C++ takes months if not years.
I agree with @tomto66 here. If you’re the type of person who learns well from books, I would highly recommend Designing Audio Effect Plug-Ins in C++ from Will Pirkle - it was instrumental when I was starting out and the concepts and techniques presented in the book allow to draw “aha” type parallels from the JUCE framework.