if you are college student what language you need to learn?

you have javascript, python, c++ and java.
You have 4 years in college?
so you need to focus on which language?

python is very easy to learn and master. So python should be your first choice.
If programming is not problem for you. You can start with any language.

**Now how to learn all these languages? Youtube , books or udemy?
Learning in our modern era is not a problem any more. And anyone is willing to teach you. You just need to be a person who is willing to learn all the time. So just start learning. You have tons of learning platforms. We have both free and paid platforms.
Free platform#
w3school,tutorial points is text base tutorials platform, completely free.
youtube is totally free as you know

Paid Platforms#
Lynda(LinkedIn learning) , skillShare and udemy are paid platforms.
Udemy has tons of free resources available and you use it lifetime.
Paid course are not very expensive and some great courses are available for $10 to 20.

Should I learn all programming languages ?
No you don’t need to learn all langauges. If you focus on main languages it will be enough for you. Top languages are C++ , Java, Python and Javascript. One thing more. If you focus on just one. it will be enough for you. And You generate tons of money with it.

What strategy should I follow If I want to learn all of these languages ?

You have four years in college. so If you pick 1 language per year will be great choice.

let suppose you start with JavaScript and Started learning it from scratch. Dedicate one year for JS.

After completion of 1st year you can focus on language. Let suppose we choose python for 2nd year and start learnig it and cover all the aspects in one year. or may be half of the concepts.

3rd year we are left with 2 choices java and c++. Now you have grasped all the fundamentals and Now you are ready to learn any language. Hope so it will not be that much difficult. You can choose any of these two java or C++. You start learning it. Learning programming language may not be difficult for you. You have already mastered javascript and python. So most of the concept are same. just syntax is change. It is not problem for you any more.