An Interactive Q&A Forum
You can choose whatever suits you, explore on your own,i can give a lengthy lecture on what to do and what not to do, but untill and unless you explore,discover and learn on your own it would be of no use, thats what i learnt from my coding idol in college.
And now for the direct answer-
1) learn how to code at first
2) learn how to code better(algorithms)
3) ask help from senior, whenever stuck
4) there are plenty of platforms available, stick to one
Is c++ better than other programing languages for competitive coding ???
In speed yes.
In terms of clean formatted code not the best.
If a problem statement has just mathematical solution of O(1), O(n) or O(nlogn) and input is around 10^4 ,then i use python , its takes less time to complete it
Anything with input range of 10^6 + , i go to cpp, if the time constraint is really tight then i go for cpp even for simpler solutions involving recursion.
Then involving speed you can tweak the general settings for compiler or interpreters to get more high i/o speed or make your custom i/o template, since i/o makes a significant impact in speed and can be controlled unlike to computational speed
Google search would help you better.
Not having a vast idea but you can start on HackerRank Platform.