I want to learn c++ language. What should I do first ?

Answer 1

Complete the course here first, then read some books on intermediate and advanced C++.

Some books you can use later :

>> The C++ Programming Language - Bjarne Stroustrup
>> Effective C++ - Scott Meyers

For other suggestions, use this definitive list : https://stackoverflow.com/questions/388242/the-definitive-c-book-guide-and-list

You can also visit reference sites to learn about specific headers or functions. Some of these sites are :

en.cppreference.com/w/cpp
www.cplusplus.com
www.isocpp.com

Also, you can visit video tutorials and blogs whenever you feel stuck.

Answer 2

The SoloLearn C++ course has an old teaching approach, teaches outdated features and ways to solve problems and is far too short.
You can ask questions here, though.
For the rest, I agree with Kinshuk Vasisht.

Answer 3

brush up on your math. 😬
jk ...SoloLearn is a great start