Don't get much confused, things are much simpler than you probably think to get confused.
If you know c++ that is good you can still go thru C for understanding. many times coding in C is simpler than in C++.
My personal opinion. C or C++, it depends what is your application.
For PC or other high-end MPU/MCU, C++ may be more popular.
For low-end MCU, such as PIC or 8051, C is still popular than C++. Or only C compiler is availble.