This is a collection of C and C++ books and resources that are either available online or you can also download a pdf or other formats C A Tutorial on Pointers and Arrays in C Advanced Linux Programming Beej's Guide to C Programming Beej's Guide...
C#
This is a useful list of compilers, build systems and IDE's for C++ Compiler List of C or C++ compilers 8cc - A Small C Compiler. c - Compile and execute C.
There are a lot of great resources on youtube for C#, you don't have to pay for some expensive course with some of our suggestions below there are literally hours.