PX4 Programming Languages

May I know what languages to develop PX4 flight controllers software? C and C++?
What are the best way to learn about them??

Mainly C++, you can checkout some documentation here:

Thank you. Our aircraft is innovative using new air frame that I don’t see mentioning. Basically it’s airplane with rotary wing.
Either C or C++ is overwhelming so we need to hire a qualified person. Please let me know if you or anyone can help of course with pay.