Start with online tutorials to understand the basics. Here are some:
- https://www.w3schools.com/c/
- https://www.learn-c.org/
- https://www.geeksforgeeks.org/c/c-programming-language/
Then, start doing some easier exercises and learn along the way. Here are some ideas:
- Guess my number: the computer "thinks of" a number, and the user has to guess it by entering a number, and the computer will tell if the number is less or equal to it.
- List all the primes up to N.
- Create a hangman game.
- Create a catalog tool, for instance, car parts, or a car rental system, or a store, etc.
- Create a tool that tracks who spent how much in that month and how to share the expenditures (this can be a pretty useful stuff in a household. It would save a lot of time for your parents if they do not have a shared bank account. I wrote one of these stuff and reduced my monthly budget calculation time to just a few minutes.
The point is, to start to put your skills into practical use, either through toy projects or actual projects that make your (or your family's/friends') everyday life easier.
You can always keep the C/C++ reference handy, such as
- https://cppreference.com/
- https://cplusplus.com/reference/
Good luck and enjoy your journey!